FETCHMAIL(1) fetchmail 6.5.1 FETCHMAIL(1)
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NAME
fetchmail - fetch mail from a POP, IMAP, ETRN, or ODMR-capable server
SYNOPSIS
fetchmail [option...] [mailserver...]
fetchmailconf
DESCRIPTION
fetchmail is a mail-retrieval and forwarding utility; it fetches mail
from remote mail servers and forwards it to your local (client)
machine's delivery system. You can then handle the retrieved mail
using normal mail user agents such as mutt(1), elm(1) or Mail(1). The
fetchmail utility can be run in a daemon mode to repeatedly poll one
or more systems at a specified interval.
The fetchmail program can gather mail from servers supporting any of
the common mail-retrieval protocols: POP2 (legacy, to be removed from
future release), POP3, IMAP2bis, IMAP4, and IMAP4rev1. It can also
use the ESMTP ETRN extension and ODMR. (The RFCs describing all these
protocols are listed at the end of this manual page.)
While fetchmail is primarily intended to be used over on-demand TCP/IP
links (such as SLIP or PPP connections), it may also be useful as a
message transfer agent for sites which refuse for security reasons to
permit (sender-initiated) SMTP transactions with sendmail.
DEPRECATION AND CRYPTOGRAPHIC SECURITY WARNINGS
Several cryptographic algorithms that are referenced by mail
standareds for authentication were based on MD4 or MD5 or SHA1
algorithms that were developed in 1990, 1991 and 1995 respectively.
30 years later, these are no longer deemed secure, and are considered
broken.
Not all IETF standards and RFCs have given up on them, and some
protocols actively require something that incorporates MD4, MD5 or
SHA1 in some form so disabling their use in fetchmail altogether would
also pull the plug on, say, protocols such as ODMR, or formerly-
popular authentication schemes such as POP3 with APOP.
The recommendation is to prefer TLS-wrapped connections via dedicated
ports 993 (IMAP4) or 995 (POP3) or STARTTLS in-band negotiation with
such authentication schemes, to reduce the risk to expose login
credentials.
Also, weak authentication schemes will be phased out from future
fetchmail releases, please see the NEWS file that should have come
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with your distribution of fetchmail.
SUPPORT, TROUBLESHOOTING
For troubleshooting, tracing and debugging, you need to increase
fetchmail's verbosity to actually see what happens. To do that, please
run both of the two following commands, adding all of the options
you'd normally use.
env LC_ALL=C fetchmail -V -v --nodetach --nosyslog
(This command line prints in English how fetchmail understands
your configuration.)
env LC_ALL=C fetchmail -vvv --nodetach --nosyslog
(This command line actually runs fetchmail with verbose English
output.)
Also see item #G3 in fetchmail's FAQ
You can omit the LC_ALL=C part above if you want output in the local
language (if supported). However if you are posting to mailing lists,
please leave it in. The maintainers do not necessarily understand your
language, please use English.
QUICKSTART
1. Set up a local SMTP mail server, or command-line based mail
delivery agent such as maildrop or dovecot-lda, configure and test and
debug it. Make sure that mail you deliver to yourself through it ends
up in the right place. Do NOT continue unless and until this works or
you risk losing mail!
2. Create a .fetchmailrc file in your home directory that looks
roughly like this, for POP3 fetches.
poll mailserver.example.org proto POP3 uidl
user joe.sixpack
keep ssl
You need to adjust several elements here: mailserver.example.org is
the server's name. joe.sixpack is the login name to use for the
server. keep states that messages should be left on the server,
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rather than deleted. ssl states that the connection should be
encrypted. If you need to use IMAP instead of POP3, change "proto
POP3 uidl" to "proto IMAP".
If you chose to deliver through a command-line program, add an mda
option, for instance:
mda "/usr/bin/maildrop -d %T"
3. And then make sure the ~/.fetchmailrc file is not readable or
writable to anyone but yourself:
chmod 0600 ~/.fetchmailrc
4. Finally, run fetchmail in verbose mode and see that it works. To
limit impact, if something goes wrong, we just try two messages:
fetchmail -v --fetchlimit 2
If then the POP3 server refuses UIDL, you cannot use the "keep" option
on that server and you need to remove the uidl and keep options, but
note that then fetchmail will remove messages it has successfully
delivered from the server.
TLS (SSL) QUICKSTART
Your fetchmail distribution should have come with a README.SSL file,
which see. It is recommended to configure all polls with --ssl --
sslproto tls1.2+ if supported by the server, which configures
fetchmail along recent IETF proposed standards and best current
practices, RFC-8314, RFC-8996, RFC-8997.
CONCEPTS
If fetchmail is used with a POP or an IMAP server (but not with ETRN
or ODMR), it has two fundamental modes of operation for each user
account from which it retrieves mail: singledrop- and multidrop-mode.
In singledrop-mode,
fetchmail assumes that all messages in the user's account
(mailbox) are intended for a single recipient. The identity of
the recipient will either default to the local user currently
executing fetchmail, or will need to be explicitly specified in
the configuration file.
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fetchmail uses singledrop-mode when the fetchmailrc configuration
contains at most a single local user specification for a given
server account.
In multidrop-mode,
fetchmail assumes that the mail server account actually contains
mail intended for any number of different recipients. Therefore,
fetchmail must attempt to deduce the proper "envelope recipient"
from the mail headers of each message. In this mode of
operation, fetchmail almost resembles a mail transfer agent
(MTA).
Note that neither the POP nor IMAP protocols were intended for
use in this fashion, and hence envelope information is often not
directly available. The ISP must store the envelope information
in some message header and. The ISP must also store one copy of
the message per recipient. If either of the conditions is not
fulfilled, this process is unreliable, because fetchmail must
then resort to guessing the true envelope recipient(s) of a
message. This usually fails for mailing list messages and Bcc:d
mail, or mail for multiple recipients in your domain.
fetchmail uses multidrop-mode when more than one local user
and/or a wildcard is specified for a particular server account in
the configuration file.
In ETRN and ODMR modes,
these considerations do not apply, as these protocols are based
on SMTP, which provides explicit envelope recipient information.
These protocols always support multiple recipients.
As each message is retrieved, fetchmail normally delivers it via SMTP
to port 25 on the machine it is running on (localhost), just as though
it were being passed in over a normal TCP/IP link. fetchmail provides
the SMTP server with an envelope recipient derived in the manner
described previously. The mail will then be delivered according to
your MTA's rules (the Mail Transfer Agent is usually sendmail(8),
exim(8), or postfix(8)). Invoking your system's MDA (Mail Delivery
Agent) is the duty of your MTA. All the delivery-control mechanisms
(such as .forward files) normally available through your system MTA
and local delivery agents will therefore be applied as usual.
If your fetchmail configuration sets a local MDA (see the --mda
option), it will be used directly instead of talking SMTP to port 25.
If the program fetchmailconf is available, it will assist you in
setting up and editing a fetchmailrc configuration. It runs under the
X window system and requires that the language Python and the Tk
toolkit (with Python bindings) be present on your system. If you are
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first setting up fetchmail for single-user mode, it is recommended
that you use Novice mode. Expert mode provides complete control of
fetchmail configuration, including the multidrop features. In either
case, the 'Autoprobe' button will tell you the most capable protocol a
given mail server supports, and warn you of potential problems with
that server.
PREFACE ON THIS MANUAL
Fetchmail's run-time strings have been translated (localized) to some
languages, but the manual is only available in English. In some
situations, for comparing output to manual, it may be helpful to
switch fetchmail to English output by overriding the locale variables,
for instance:
env LC_ALL=C fetchmail # add other options before the hash
env LANG=en fetchmail # other options before the hash
or similar. Details vary by operating system.
GENERAL OPERATION
The behavior of fetchmail is controlled by command-line options and a
run control file, ~/.fetchmailrc, the syntax of which we describe in a
later section (this file is what the fetchmailconf program edits).
Command-line options override ~/.fetchmailrc declarations.
Each server name that you specify following the options on the command
line will be queried. If you do not specify any servers on the
command line, each 'poll' entry in your ~/.fetchmailrc file will be
queried, unless the idle option is used, which see.
To facilitate the use of fetchmail in scripts and pipelines, it
returns an appropriate exit code upon termination -- see EXIT CODES
below.
The following options modify the behavior of fetchmail. It is seldom
necessary to specify any of these once you have a working .fetchmailrc
file set up.
Almost all options have a corresponding keyword which can be used to
declare them in a .fetchmailrc file.
Some special options are not covered here, but are documented instead
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in sections on AUTHENTICATION and DAEMON MODE which follow.
General Options
-? | --help
Displays option help.
-V | --version
Displays the version information for your copy of fetchmail. No
mail fetch is performed. Instead, for each server specified, all
the option information that would be computed if fetchmail were
connecting to that server is displayed. Any non-printable
characters in passwords or other string names are shown as back-
slashed C-like escape sequences. This option is useful for
verifying that your options are set the way you want them.
-c | --check
Return a status code to indicate whether there is mail waiting,
without actually fetching or deleting mail (see EXIT CODES
below). This option turns off daemon mode (in which it would be
useless). It does not play well with queries to multiple sites,
and does not work with ETRN or ODMR. It will return a false
positive if you leave read but undeleted mail in your server
mailbox and your fetch protocol cannot tell kept messages from
new ones. This means it will work with IMAP, not work with POP2,
and may occasionally flake out under POP3.
-s | --silent
Silent mode. Suppresses all progress/status messages that are
normally echoed to standard output during a fetch (but does not
suppress actual error messages). The --verbose option overrides
this.
-v | --verbose
Verbose mode. All control messages passed between fetchmail and
the mail server are echoed to stdout. Overrides --silent.
Doubling this option (-v -v) causes extra diagnostic information
to be printed.
--nosoftbounce
(since v6.3.10, Keyword: set no softbounce, since v6.3.10)
Hard bounce mode. All permanent delivery errors cause messages to
be deleted from the upstream server, see "no softbounce" below.
--softbounce
(since v6.3.10, Keyword: set softbounce, since v6.3.10)
Soft bounce mode. All permanent delivery errors cause messages to
be left on the upstream server if the protocol supports that.
This option is on by default and will be changed to hard bounce
mode in the next fetchmail release.
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Disposal Options
-a | --all | (since v6.3.3)
(Keyword: fetchall, since v3.0)
Retrieve both old (seen) and new messages from the mail server.
The default is to fetch only messages the server has not marked
seen. Under POP3, this option also forces the use of RETR rather
than TOP. Note that POP2 retrieval behaves as though --all is
always on (see RETRIEVAL FAILURE MODES below) and this option
does not work with ETRN or ODMR. While the -a and --all
command-line and fetchall rcfile options have been supported for
a long time, the --fetchall command-line option was added in
v6.3.3.
-k | --keep
(Keyword: keep)
Keep retrieved messages on the remote mail server. Normally,
messages are deleted from the folder on the mail server after
they have been retrieved. Specifying the keep option causes
retrieved messages to remain in your folder on the mail server.
This option does not work with ETRN or ODMR. If used with POP3,
it is recommended to also specify the --uidl option or uidl
keyword.
-K | --nokeep
(Keyword: nokeep)
Delete retrieved messages from the remote mail server. This
option forces retrieved mail to be deleted. It may be useful if
you have specified a default of keep in your .fetchmailrc. This
option is forced on with ETRN and ODMR.
--moveto <folder>
(Keyword: moveto)
In IMAP mode, instead of flushing a message, move it to the given
IMAP folder instead. This is useful for avoiding data loss while
testing, and is the preferred way to delete emails on certain
implementations, for example Google wants you to delete mails by
moving them to [Gmail]/Trash. Only available for IMAP servers.
This option is only accepted with --proto imap, but not if IMAP
is chosen automatically. It is ineffective when --keep is in
effect.
-F | --flush
(Keyword: flush)
POP3/IMAP only. This is a dangerous option and can cause mail
loss when used improperly. It deletes old (seen) messages from
the mail server before retrieving new messages. Warning: This
can cause mail loss if you check your mail with other clients
than fetchmail, and cause fetchmail to delete a message it had
never fetched before. It can also cause mail loss if the mail
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server marks the message seen after retrieval (IMAP2 servers).
You should probably not use this option in your configuration
file. If you use it with POP3, you must use the 'uidl' option.
What you probably want is the default setting: if you do not
specify '-k', then fetchmail will automatically delete messages
after successful delivery.
--limitflush
POP3/IMAP only, since version 6.3.0. Delete oversized messages
from the mail server before retrieving new messages. The size
limit should be separately specified with the --limit option.
This option does not work with ETRN or ODMR.
Protocol and Query Options
-p <proto> | --proto <proto> |
(Keyword: proto[col])
Specify the protocol to use when communicating with the remote
mail server. If no protocol is specified, the default is AUTO.
proto may be one of the following:
AUTO Tries IMAP, POP3, and POP2 (skipping any of these for which
support has not been compiled in).
POP2 Post Office Protocol 2 (legacy, to be removed from future
release)
POP3 Post Office Protocol 3
APOP Use POP3 with old-fashioned MD5-challenge authentication.
Considered not resistant to man-in-the-middle attacks.
RPOP Use POP3 with RPOP authentication.
KPOP Use POP3 with Kerberos V4 authentication on port 1109.
SDPS Use POP3 with Demon Internet's SDPS extensions.
IMAP IMAP2bis, IMAP4, or IMAP4rev1 (fetchmail automatically
detects their capabilities).
ETRN Use the ESMTP ETRN option.
ODMR Use the On-Demand Mail Relay ESMTP profile.
All these alternatives work in basically the same way (communicating
with standard server daemons to fetch mail already delivered to a
mailbox on the server) except ETRN and ODMR. The ETRN mode allows you
to ask a compliant ESMTP server (such as BSD sendmail at release 8.8.0
or higher) to immediately open a sender-SMTP connection to your client
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machine and begin forwarding any items addressed to your client
machine in the server's queue of undelivered mail. The ODMR mode
requires an ODMR-capable server and works similarly to ETRN, except
that it does not require the client machine to have a static DNS.
-U | --uidl
(Keyword: uidl)
Force UIDL use (effective only with POP3). Force client-side
tracking of 'newness' of messages (UIDL stands for "unique ID
listing" and is described in RFC1939). Use with 'keep' to use a
mailbox as a baby news drop for a group of users. The fact that
seen messages are skipped is logged, unless error logging is done
through syslog while running in daemon mode. Note that fetchmail
may automatically enable this option depending on upstream server
capabilities. Note also that this option may be removed and
forced enabled in a future fetchmail version. See also: --idfile.
--idle (since 6.3.3)
(Keyword: idle, since before 6.0.0)
Enable IDLE use (effective only with IMAP). Note that this works
with only one account and one folder at a given time, other
folders or accounts will not be polled when idle is in effect!
While the idle rcfile keyword had been supported for a long time,
the --idle command-line option was added in version 6.3.3. IDLE
use means that fetchmail tells the IMAP server to send notice of
new messages, so they can be retrieved sooner than would be
possible with regular polls.
--forceidle (since 6.5.0)
(Keyword: forceidle, since 6.5.0)
Use IDLE even if the server does not advertise it in their
capabilities. This is a dangerous option, use carefully.
--idletimeout (since 6.5.0)
(Keyword: idletimeout, since 6.5.0)
Set the timeout (in seconds) for the IDLE command because too
many servers break the protocol (which requires 30 minutes) and
hang up after a few minutes. Default value: 1680 s (= 28 min).
-P <portnumber> | --service <servicename>
(Keyword: service) Since version 6.3.0.
The service option permits you to specify a service name to
connect to. You can specify a decimal port number here, if your
services database lacks the required service-port assignments.
See the FAQ item R12 and the --ssl documentation for details.
This replaces the older --port option.
Note that this does not magically switch between TLS-wrapped and
STARTTLS modes, if you specify a port number or service name here that
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is TLS-wrapped, meaning it starts to negotiate TLS before sending
application data in the clear, you may need to specify --ssl on the
command line or ssl in your rcfile.
--port <portnumber>
(Keyword: port)
Obsolete version of --service that does not take service names.
Note: this option may be removed from a future version.
--principal <principal>
(Keyword: principal)
The principal option permits you to specify a service principal
for mutual authentication. This is applicable to POP3 or IMAP
with Kerberos 4 authentication only. It does not apply to
Kerberos 5 or GSSAPI. This option may be removed in a future
fetchmail version.
-t <seconds> | --timeout <seconds>
(Keyword: timeout)
The timeout option allows you to set a server-non-response
timeout in seconds. If a mail server does not send a greeting
message or respond to commands for the given number of seconds,
fetchmail will drop the connection to it. Without such a timeout
fetchmail might hang until the TCP connection times out, trying
to fetch mail from a down host, which may be very long. This
would be particularly annoying for a fetchmail running in the
background. There is a default timeout which fetchmail~-V will
report. If a given connection receives too many timeouts in
succession, fetchmail will consider it wedged and stop retrying.
The calling user will be notified by email if this happens.
Beginning with fetchmail 6.3.10, the SMTP client uses the
recommended minimum timeouts from RFC-5321 while waiting for the
SMTP/LMTP server it is talking to. You can raise the timeouts
even more, but you cannot shorten them. This is to avoid a
painful situation where fetchmail has been configured with a
short timeout (a minute or less), ships a long message (many
MBytes) to the local MTA, which then takes longer than timeout to
respond "OK", which it eventually will; that would mean the mail
gets delivered properly, but fetchmail cannot notice it and will
thus re-fetch this big message over and over again.
--plugin <command>
(Keyword: plugin)
The plugin option allows you to use an external program to
establish the TCP connection. This is useful if you want to use
ssh, or need some special firewall setup. The program will be
looked up in $PATH and can optionally be passed the host name and
port as arguments using "%h" and "%p" respectively (note that the
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interpolation logic is rather primitive, and these tokens must be
bounded by whitespace or beginning of string or end of string).
Fetchmail will write to the plugin's stdin and read from the
plugin's stdout.
--plugout <command>
(Keyword: plugout)
Identical to the plugin option above, but this one is used for
the SMTP connections.
-r <name> | --folder <name>
(Keyword: folder[s])
Causes a specified non-default mail folder on the mail server (or
comma-separated list of folders) to be retrieved. The syntax of
the folder name is server-dependent. This option is not
available under POP3, ETRN, or ODMR.
--tracepolls
(Keyword: tracepolls)
Tell fetchmail to poll trace information in the form 'polling
account %s' and 'folder %s' to the Received line it generates,
where the %s parts are replaced by the user's remote name, the
poll label, and the folder (mailbox) where available (the
Received header also normally includes the server's true name).
This can be used to facilitate mail filtering based on the
account it is being received from. The folder information is
written only since version 6.3.4.
--ssl
(Keyword: ssl)
Causes the connection to the mail server to be encrypted via SSL,
by negotiating SSL directly after connecting (called SSL-wrapped
mode, or Implicit TLS by RFC-8314). Please see the description
of --sslproto below! More information is available in the
README.SSL file that ships with fetchmail.
Note that even if this option is omitted, fetchmail may still
negotiate SSL in-band for POP3 or IMAP, through the STLS or
STARTTLS feature. You can use the --sslproto option to modify
that behavior.
If no port is specified, the connection is attempted to the well
known port of the SSL version of the base protocol. This is
generally a different port than the port used by the base
protocol. For IMAP, this is port 143 for the clear protocol and
port 993 for the SSL secured protocol; for POP3, it is port 110
for the clear text and port 995 for the encrypted variant.
If your system lacks the corresponding entries from
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/etc/services, see the --service option and specify the numeric
port number as given in the previous paragraph (unless your ISP
had directed you to different ports, which is uncommon however).
--nossl
(Keyword: nossl)
Cancels out a default of ssl given earlier, in defaults, or in an
rcfile if --nossl is given on the command-line. Use --sslproto
with proper argument to enable STARTTLS.
--sslcert <name>
(Keyword: sslcert)
For certificate-based client authentication. Some SSL encrypted
servers require client side keys and certificates for
authentication. In most cases, this is optional. This specifies
the location of the public key certificate to be presented to the
server at the time the SSL session is established. It is not
required (but may be provided) if the server does not require it.
It may be the same file as the private key (combined key and
certificate file) but this is not recommended. Also see --sslkey
below.
NOTE: If you use client authentication, the user name is fetched
from the certificate's CommonName and overrides the name set with
--user.
--sslkey <name>
(Keyword: sslkey)
Specifies the file name of the client side private SSL key. Some
SSL encrypted servers require client side keys and certificates
for authentication. In most cases, this is optional. This
specifies the location of the private key used to sign
transactions with the server at the time the SSL session is
established. It is not required (but may be provided) if the
server does not require it. It may be the same file as the public
key (combined key and certificate file) but this is not
recommended.
If a password is required to unlock the key, it will be prompted
for at the time just prior to establishing the session to the
server. This can cause some complications in daemon mode.
Also see --sslcert above.
--sslproto <value>
(Keyword: sslproto, NOTE: semantic changes since v6.4.0)
This option has a dual use, out of historic fetchmail behaviour.
It controls both the SSL/TLS protocol version and, if --ssl is
not specified, the STARTTLS behaviour (upgrading the protocol to
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an SSL or TLS connection in-band). Some other options may however
make TLS mandatory -- in particular, --sslcertck is now default
behavior and requires SSL.
Recognized values for --sslproto are given below. You should
normally choose one of the auto-negotiating options, i. e.
'tls1.2+' or 'auto' or one of the other options ending in a plus
(+) character. Note that depending on OpenSSL library version
and configuration, some options cause run-time errors because the
requested SSL or TLS versions are not supported by the particular
installed OpenSSL library. Test well before you deploy for
unattended operation.
'auto'
(default, the same as TLS1.2+). Since v6.4.0, changed in
v6.5.0. Require TLS. Auto-negotiate TLSv1.2 or newer,
disable downgrade below. (older fetchmail versions than
v6.5.0 have auto-negotiated older protocols, v6.4.x would
permit TLSv1.0 by default, v6.3.x would permit SSLv3).
'', the empty string
Disable STARTTLS. If --ssl is given for the same server, log
an error and pretend that 'auto' had been used instead.
'SSL23'
see 'auto'. Deprecated, recognized for backwards
compatibility.
'TLS'
see 'auto'. For symmetry with OpenSSL client method names.
'TLS1'
Require TLSv1. This does not negotiate TLSv1.1 or newer, and
is discouraged. Replace by TLS1+ unless the latter chokes
your server.
'TLS1+'
Since v6.4.0. This is an auto-negotiation feature that will
permit TLSv1.0 and newer.
'TLS1.1'
Since v6.4.0. Require TLS v1.1 exactly.
'TLS1.1+'
Since v6.4.0. Require TLS. Auto-negotiate TLSv1.1 or newer.
'TLS1.2'
Since v6.4.0. Require TLS v1.2 exactly.
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'TLS1.2+'
Since v6.4.0. Require TLS. Auto-negotiate TLSv1.2 or newer.
This is the default in fetchmail v6.5.x.
'TLS1.3'
Since v6.4.0. Require TLS v1.3 exactly.
'TLS1.3+'
Since v6.4.0. Require TLS. Auto-negotiate TLSv1.3 or newer.
Unrecognized parameters
are treated the same as 'auto'.
NOTE: you should hardly ever need to use anything other than ''
(to force an unencrypted connection) or 'auto' (to enforce TLS).
--sslcertck
(Keyword: sslcertck, default enabled since v6.4.0)
--sslcertck causes fetchmail to require that disconnect unless it
can successfully negotiate SSL or TLS, or if it cannot
successfully verify and validate the certificate and follow it to
a trust anchor (or trusted root certificate). The trust anchors
are given as a set of local trusted certificates (see the
sslcertfile and sslcertpath options). If the server certificate
cannot be obtained or is not signed by one of the trusted ones
(directly or indirectly), fetchmail will disconnect, regardless
of the sslfingerprint option.
--nosslcertck
(Keyword: no sslcertck, only in v6.4.X)
The opposite of --sslcertck, this is a discouraged option. It
permits fetchmail to continue connecting even if the server
certificate failed the verification checks. Should only be used
together with --sslfingerprint.
--sslcertfile <file>
(Keyword: sslcertfile, since v6.3.17)
Sets the file fetchmail uses to look up local certificates. The
default is empty. This can be given in addition to --sslcertpath
below, and certificates specified in --sslcertfile will be
processed before those in --sslcertpath. The option can be used
in addition to --sslcertpath.
The file is a text file. It contains the concatenation of trusted
CA certificates in PEM format.
Note that using this option will suppress loading the default SSL
trusted CA certificates file unless you set the environment
variable FETCHMAIL_INCLUDE_DEFAULT_X509_CA_CERTS to a non-empty
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value.
--sslcertpath <directory>
(Keyword: sslcertpath)
Sets the directory fetchmail uses to look up local certificates.
The default is your OpenSSL default directory. The directory must
be hashed the way OpenSSL expects it - every time you add or
modify a certificate in the directory, you need to use the
c_rehash tool (which comes with OpenSSL in the tools/ sub-
directory). Also, after OpenSSL upgrades, you may need to run
c_rehash.
This can be given in addition to --sslcertfile above, which see
for precedence rules.
Note that using this option will suppress adding the default SSL
trusted CA certificates directory unless you set the environment
variable FETCHMAIL_INCLUDE_DEFAULT_X509_CA_CERTS to a non-empty
value.
--sslcommonname <common name>
(Keyword: sslcommonname; since v6.3.9)
Use of this option is discouraged. Before using it, contact the
administrator of your upstream server and ask for a proper SSL
certificate to be used. If that cannot be attained, this option
can be used to specify the name (CommonName) that fetchmail
expects on the server certificate. A correctly configured server
will have this set to the host name by which it is reached, and
by default fetchmail will expect as much. Use this option when
the CommonName is set to some other value, to avoid the "Server
CommonName mismatch" warning, and only if the upstream server's
operator cannot be made to use proper certificates.
--sslfingerprint [{<algo>}]<fingerprint>
(Keyword: sslfingerprint)
Specify the fingerprint of the server key in hexadecimal notation
with colons separating groups of two digits. This is the format
that fetchmail uses to report the fingerprint when an SSL
connection is established. When this is specified, fetchmail
will compare the server key fingerprint with the given one, and
the connection will fail if they do not match, regardless of the
sslcertck setting. The connection will also fail if fetchmail
cannot obtain an SSL certificate from the server. This can be
used to prevent man-in-the-middle attacks, but the finger print
from the server must be obtained or verified over a secure
channel, and certainly not over the same Internet connection that
fetchmail would use.
The fingerprint can be prefixed with an EVP_MD digest algorithm
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name in curly braces, for instance, {MD5}00:01:...:0F. All
digest algorithms that your SSL provider library supports can be
used. Choose a sensible one, for instance, SHA256. If the
{algo} prefix is omitted, MD5 is used for compatibility with
fetchmail 6.4 and older.
Using this option will prevent printing certificate verification
errors as long as --nosslcertck is in effect.
If you just want the --verbose log output to switch logging to a
different hash, without pinning the server's certificate hash,
you can use --sslfingerprint '{algo}*', f.i., --sslfingerprint
'{SHA256}*'
To obtain the fingerprint of a certificate stored in the file
cert.pem, try:
openssl x509 -in cert.pem -noout -sha256 -fingerprint
For details, see x509(1ssl).
Delivery Control Options
-S <hosts> | --smtphost <hosts>
(Keyword: smtp[host])
Specify a hunt list of hosts to forward mail to (one or more host
names, comma-separated). Hosts are tried in list order; the first
one that is up becomes the forwarding target for the current run.
If this option is not specified, 'localhost' is used as the
default. Each host name may have a port number following the
host name. The port number is separated from the host name by a
slash; the default port is "smtp". If you specify an absolute
path name (beginning with a /), it will be interpreted as the
name of a UNIX socket accepting LMTP connections (such as is
supported by the Cyrus IMAP daemon) Example:
--smtphost server1,server2/2525,server3,/var/imap/socket/lmtp
This option can be used with ODMR, and will make fetchmail a
relay between the ODMR server and SMTP or LMTP receiver.
WARNING: if you use address numeric IP addresses here, be sure to
use --smtpaddress or --smtpname (either of which see) with a
valid SMTP address literal!
--fetchdomains <hosts>
(Keyword: fetchdomains)
In ETRN or ODMR mode, this option specifies the list of domains
the server should ship mail for once the connection is turned
around. The default is the FQDN of the machine running
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fetchmail.
-D <domain> | --smtpaddress <domain>
(Keyword: smtpaddress)
Specify the domain to be appended to addresses in RCPT TO lines
shipped to SMTP. When this is not specified, the name of the SMTP
server (as specified by --smtphost) is used for SMTP/LMTP and
'localhost' is used for UNIX socket/BSMTP.
NOTE: if you intend to use numeric addresses, or so-called
address literals per the SMTP standard, write them in proper SMTP
syntax, for instance --smtpaddress "[192.0.2.6]" or --smtpaddress
"[IPv6:2001:DB8::6]".
--smtpname <user@domain>
(Keyword: smtpname)
Specify the domain and user to be put in RCPT TO lines shipped to
SMTP. The default user is the current local user. Please also
see the NOTE about --smtpaddress and address literals above.
-Z <nnn> | --antispam <nnn[, nnn]...>
(Keyword: antispam)
Specifies the list of numeric SMTP errors that are to be
interpreted as a spam-block response from the listener. A value
of -1 disables this option. For the command-line option, the
list values should be comma-separated. Note that the antispam
values only apply to "MAIL FROM" responses in the SMTP/LMTP
dialogue, but several MTAs (Postfix in its default configuration,
qmail) defer the anti-spam response code until after the RCPT TO.
--antispam does not work in these circumstances. Also see
--softbounce (default) and its inverse.
-m <command> | --mda <command>
(Keyword: mda)
This option lets fetchmail use a Message or Local Delivery Agent
(MDA or LDA) directly, rather than forward via SMTP or LMTP.
To avoid losing mail, use this option only with MDAs like
maildrop or MTAs like sendmail that exit with a nonzero status on
disk-full and other delivery errors; the nonzero status tells
fetchmail that delivery failed and prevents the message from
being deleted on the server.
If fetchmail is running as root, it sets its user id while
delivering mail through an MDA as follows: First, the
FETCHMAILUSER, LOGNAME, and USER environment variables are
checked in this order. The value of the first variable from his
list that is defined (even if it is empty!) is looked up in the
system user database. If none of the variables is defined,
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fetchmail will use the real user id it was started with. If one
of the variables was defined, but the user stated there is not
found, fetchmail continues running as root, without checking
remaining variables on the list. Practically, this means that if
you run fetchmail as root (not recommended), it is most useful to
define the FETCHMAILUSER environment variable to set the user
that the MDA should run as. Some MDAs (such as maildrop) are
designed to be setuid root and setuid to the recipient's user id,
so you do not lose functionality this way even when running
fetchmail as unprivileged user. Check the MDA's manual for
details.
Some possible MDAs are "/usr/sbin/sendmail -i -f %F -- %T" (Note:
some several older or vendor sendmail versions mistake -- for an
address, rather than an indicator to mark the end of the option
arguments), "/usr/bin/deliver" and "/usr/bin/maildrop -d %T".
Local delivery addresses will be inserted into the MDA command
wherever you place a %T; the mail message's From address will be
inserted where you place an %F.
Do NOT enclose the %F or %T string in single quotes! For both %T
and %F, fetchmail encloses the addresses in single quotes ('),
after removing any single quotes they may contain, before the MDA
command is passed to the shell.
Do NOT use an MDA invocation that dispatches on the contents of
To/Cc/Bcc, like "sendmail -i -t" or "qmail-inject", it will
create mail loops and bring the just wrath of many postmasters
down upon your head. This is one of the most frequent
configuration errors!
Also, do not try to combine multidrop mode with an MDA such as
maildrop that can only accept one address, unless your upstream
stores one copy of the message per recipient and transports the
envelope recipient in a header; you will lose mail.
The well-known procmail(1) package is very hard to configure
properly, it has a very nasty "fall through to the next rule"
behavior on delivery errors (even temporary ones, such as out of
disk space if another user's mail daemon copies the mailbox
around to purge old messages), so your mail will end up in the
wrong mailbox sooner or later. The proper procmail configuration
is outside the scope of this document. Using maildrop(1) is
usually much easier, and many users find the filter syntax used
by maildrop easier to understand.
Finally, we strongly advise that you do not use qmail-inject.
The command line interface is non-standard without providing
benefits for typical use, and fetchmail makes no attempts to
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accommodate qmail-inject's deviations from the standard. Some of
qmail-inject's command-line and environment options are actually
dangerous and can cause broken threads, non-detected duplicate
messages and forwarding loops.
--lmtp
(Keyword: lmtp)
Cause delivery via LMTP (Local Mail Transfer Protocol). A
service host and port must be explicitly specified on each host
in the smtphost hunt list (see above) if this option is selected;
the default port 25 will (in accordance with RFC 2033) not be
accepted.
--bsmtp <filename>
(Keyword: bsmtp)
Append fetched mail to a BSMTP file. This simply contains the
SMTP commands that would normally be generated by fetchmail when
passing mail to an SMTP listener daemon.
An argument of '-' causes the SMTP batch to be written to
standard output, which is of limited use: this only makes sense
for debugging, because fetchmail's regular output is interspersed
on the same channel, so this is not suitable for mail delivery.
This special mode may be removed in a later release.
Note that fetchmail's reconstruction of MAIL FROM and RCPT TO
lines is not guaranteed correct; the caveats discussed under THE
USE AND ABUSE OF MULTIDROP MAILBOXES below apply. This mode has
precedence before --mda and SMTP/LMTP.
--bad-header {reject|accept}
(Keyword: bad-header; since v6.3.15)
Specify how fetchmail is supposed to treat messages with bad
headers, i.e., headers with bad syntax. Traditionally, fetchmail
has rejected such messages, but some distributors modified
fetchmail to accept them. You can now configure fetchmail's
behaviour per server.
Resource Limit Control Options
-l <maxbytes> | --limit <maxbytes>
(Keyword: limit)
Takes a maximum octet size argument, where 0 is the default and
also the special value designating "no limit". If nonzero,
messages larger than this size will not be fetched and will be
left on the server (in foreground sessions, the progress messages
will note that they are "oversized"). If the fetch protocol
permits (in particular, under IMAP or POP3 without the fetchall
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option) the message will not be marked seen.
An explicit --limit of 0 overrides any limits set in your run
control file. This option is intended for those needing to
strictly control fetch time due to expensive and variable phone
rates.
Combined with --limitflush, it can be used to delete oversized
messages waiting on a server. In daemon mode, oversize
notifications are mailed to the calling user (see the --warnings
option). This option does not work with ETRN or ODMR.
-w <interval> | --warnings <interval>
(Keyword: warnings)
Takes an interval in seconds. When you call fetchmail with a
'limit' option in daemon mode, this controls the interval at
which warnings about oversized messages are mailed to the calling
user (or the user specified by the 'postmaster' option). One
such notification is always mailed at the end of the first poll
that the oversized message is detected. Thereafter, re-
notification is suppressed until after the warning interval
elapses (it will take place at the end of the first following
poll).
-b <count> | --batchlimit <count>
(Keyword: batchlimit)
Specify the maximum number of messages that will be shipped to an
SMTP listener before the connection is deliberately torn down and
rebuilt (defaults to 0, meaning no limit). An explicit
--batchlimit of 0 overrides any limits set in your run control
file. While sendmail(8) normally initiates delivery of a message
immediately after receiving the message terminator, some SMTP
listeners are not so prompt. MTAs like smail(8) may wait till
the delivery socket is shut down to deliver. This may produce
annoying delays when fetchmail is processing very large batches.
Setting the batch limit to some nonzero size will prevent these
delays. This option does not work with ETRN or ODMR.
-B <number> | --fetchlimit <number>
(Keyword: fetchlimit)
Limit the number of messages accepted from a given server in a
single poll. By default there is no limit. An explicit
--fetchlimit of 0 overrides any limits set in your run control
file. This option does not work with ETRN or ODMR.
--fetchsizelimit <number>
(Keyword: fetchsizelimit)
Limit the number of sizes of messages accepted from a given
server in a single transaction. This option is useful in
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reducing the delay in downloading the first mail when there are
too many mails in the mailbox. By default, the limit is 100. If
set to 0, sizes of all messages are downloaded at the start.
This option does not work with ETRN or ODMR. For POP3, the only
valid non-zero value is 1.
--fastuidl <number>
(Keyword: fastuidl)
Do a binary instead of linear search for the first unseen UID.
Binary search avoids downloading the UIDs of all mails. This
saves time (especially in daemon mode) where downloading the same
set of UIDs in each poll is a waste of bandwidth. The number 'n'
indicates how rarely a linear search should be done. In daemon
mode, linear search is used once followed by binary searches in
'n-1' polls if 'n' is greater than 1; binary search is always
used if 'n' is 1; linear search is always used if 'n' is 0. In
non-daemon mode, binary search is used if 'n' is 1; otherwise
linear search is used. The default value of 'n' is 4. This
option works with POP3 only.
-e <count> | --expunge <count>
(Keyword: expunge)
Arrange for deletions to be made final after a given number of
messages. Under POP2 or POP3, fetchmail cannot make deletions
final without sending QUIT and ending the session -- with this
option on, fetchmail will break a long mail retrieval session
into multiple sub-sessions, sending QUIT after each sub-session.
This is a good defense against line drops on POP3 servers. Under
IMAP, fetchmail normally issues an EXPUNGE command after each
deletion in order to force the deletion to be done immediately.
This is safest when your connection to the server is flaky and
expensive, as it avoids re-sending duplicate mail after a line
hit. However, on large mailboxes the overhead of re-indexing
after every message can slam the server pretty hard, so if your
connection is reliable it is good to do expunges less frequently.
Also note that some servers enforce a delay of a few seconds
after each quit, so fetchmail may not be able to get back in
immediately after an expunge -- you may see "lock busy" errors if
this happens. If you specify this option to an integer N, it
tells fetchmail to only issue expunges on every Nth delete. An
argument of zero suppresses expunges entirely (so no expunges at
all will be done until the end of run). This option does not
work with ETRN or ODMR.
Authentication Options
-u <name> | --user <name> |
(Keyword: user[name])
Specifies the user identification to be used when logging in to
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the mail server. The appropriate user identification is both
server and user-dependent. The default is your login name on the
client machine that is running fetchmail. See USER
AUTHENTICATION below for a complete description.
-I <specification> | --interface <specification>
(Keyword: interface)
Require that a specific interface device be up and have a
specific local or remote IPv4 (IPv6 is not supported by this
option yet) address (or range) before polling. Frequently
fetchmail is used over a transient point-to-point TCP/IP link
established directly to a mail server via SLIP or PPP. That is a
relatively secure channel. But when other TCP/IP routes to the
mail server exist (e.g., when the link is connected to an
alternate ISP), your username and password may be vulnerable to
snooping (especially when daemon mode automatically polls for
mail, shipping a clear password over the net at predictable
intervals). The --interface option may be used to prevent this.
When the specified link is not up or is not connected to a
matching IP address, polling will be skipped. The format is:
interface/iii.iii.iii.iii[/mmm.mmm.mmm.mmm]
The field before the first slash is the interface name (i.e.,
sl0, ppp0 etc.). The field before the second slash is the
acceptable IP address. The field after the second slash is a
mask which specifies a range of IP addresses to accept. If no
mask is present 255.255.255.255 is assumed (i.e., an exact
match). This option is currently only supported under Linux and
FreeBSD. Please see the monitor section for below for FreeBSD
specific information.
Note that this option may be removed from a future fetchmail
version.
-M <interface> | --monitor <interface>
(Keyword: monitor)
Daemon mode can cause transient links which are automatically
taken down after a period of inactivity (e.g., PPP links) to
remain up indefinitely. This option identifies a system TCP/IP
interface to be monitored for activity. After each poll
interval, if the link is up but no other activity has occurred on
the link, then the poll will be skipped. However, when fetchmail
is woken up by a signal, the monitor check is skipped and the
poll goes through unconditionally. This option is currently only
supported under Linux and FreeBSD. For the monitor and interface
options to work for non root users under FreeBSD, the fetchmail
binary must be installed setgid kmem. This would be a security
hole, but fetchmail runs with the effective GID set to that of
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the kmem group only when interface data is being collected.
Note that this option may be removed from a future fetchmail
version.
--auth <type>
(Keyword: auth[enticate])
This option permits you to specify an authentication type (see
USER AUTHENTICATION below for details). The possible values are
any, password, kerberos_v5, kerberos (or, for excruciating
exactness, kerberos_v4), gssapi, cram-md5, otp, ntlm, msn (only
for POP3), external (only IMAP) and implicit (ssh is understood
as alias for implicit). When any (the default) is specified,
fetchmail tries first methods that do not require a password
(EXTERNAL, GSSAPI, KERBEROS IV, KERBEROS 5); then it looks for
methods that mask your password (CRAM-MD5, NTLM, X-OTP - note
that MSN is only supported for POP3, but not auto-probed); and
only if the server does not support any of those will it ship
your password unencrypted. Other values may be used to force
various authentication methods: implicit suppresses
authentication and is thus useful for IMAP PREAUTH (if you are
using a secure --plugin, for instance, a properly configured ssh,
you may also need to set --sslproto '' or, in the rcfile,
sslproto '', in order to avoid fetchmail negotiating STARTTLS
over SSH). external suppresses authentication and is thus useful
for IMAP EXTERNAL. Any value other than password, cram-md5,
ntlm, msn or otp suppresses fetchmail's normal inquiry for a
password. Specify implicit when you are using an end-to-end
secure connection such as an ssh tunnel (in this case you may
also want to specify --sslproto '', which see); specify external
when you use TLS with client authentication and specify gssapi or
kerberos_v4 if you are using a protocol variant that employs
GSSAPI or K4. Choosing KPOP protocol automatically selects
Kerberos authentication. This option does not work with ETRN.
GSSAPI service names are in line with RFC-2743 and IANA
registrations, see Generic Security Service Application Program
Interface (GSSAPI)/Kerberos/Simple Authentication and Security
Layer (SASL) Service Names
Miscellaneous Options
-f <pathname> | --fetchmailrc <pathname>
Specify a non-default name for the ~/.fetchmailrc run control
file. The pathname argument must be either "-" (a single dash,
meaning to read the configuration from standard input) or a
filename. Unless the --version option is also on, a named file
argument must have permissions no more open than 0700
(u=rwx,g=,o=) or else be /dev/null.
-i <pathname> | --idfile <pathname>
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(Keyword: idfile)
Specify an alternate name for the .fetchids file used to save
message UIDs. NOTE: since fetchmail 6.3.0, write access to the
directory containing the idfile is required, as fetchmail writes
a temporary file and renames it into the place of the real idfile
only if the temporary file has been written successfully. This
avoids the truncation of idfiles when running out of disk space.
--pidfile <pathname>
(Keyword: pidfile; since fetchmail v6.3.4)
Override the default location of the PID file that is used as a
lock file. Default: see "ENVIRONMENT" below. Note that many
places in the code and documentation, the term "lock file" is
used. This file contains the process ID of the running fetchmail
on the first line and potentially the daemon interval on a second
line.
-n | --norewrite
(Keyword: no rewrite)
Normally, fetchmail edits RFC-822 address headers (To, From, Cc,
Bcc, and Reply-To) in fetched mail so that any mail IDs local to
the server are expanded to full addresses (@ and the mail server
host name are appended). This enables replies on the client to
get addressed correctly (otherwise your mailer might think they
should be addressed to local users on the client machine!). This
option disables the rewrite. (This option is provided to pacify
people who are paranoid about having an MTA edit mail headers and
want to know they can prevent it, but it is generally not a good
idea to actually turn off rewrite.) When using ETRN or ODMR, the
rewrite option is ineffective.
-E <line> | --envelope <line>
(Keyword: envelope; Multidrop only)
In the configuration file, an enhanced syntax is used:
envelope [<count>] <line>
This option changes the header fetchmail assumes will carry a
copy of the mail's envelope address. Normally this is
'X-Envelope-To'. Other typically found headers to carry envelope
information are 'X-Original-To' and 'Delivered-To'. Now, since
these headers are not standardized, practice varies. See the
discussion of multidrop address handling below. As a special
case, 'envelope "Received"' enables parsing of sendmail-style
Received lines. This is the default, but discouraged because it
is not fully reliable.
Note that fetchmail expects the Received-line to be in a specific
format: It must contain "by host for address", where host must
match one of the mail server names that fetchmail recognizes for
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the account in question.
The optional count argument (only available in the configuration
file) determines how many header lines of this kind are skipped.
A count of 1 means: skip the first, take the second. A count of 2
means: skip the first and second, take the third, and so on.
-Q <prefix> | --qvirtual <prefix>
(Keyword: qvirtual; Multidrop only)
The string prefix assigned to this option will be removed from
the user name found in the header specified with the envelope
option (before doing multidrop name mapping or localdomain
checking, if either is applicable). This option is useful if you
are using fetchmail to collect the mail for an entire domain and
your ISP (or your mail redirection provider) is using qmail. One
of the basic features of qmail is the Delivered-To: message
header. Whenever qmail delivers a message to a local mailbox it
puts the username and host name of the envelope recipient on this
line. The major reason for this is to prevent mail loops. To
set up qmail to batch mail for a disconnected site the ISP-
mailhost will have normally put that site in its 'Virtualhosts'
control file so it will add a prefix to all mail addresses for
this site. This results in mail sent to
'username@userhost.userdom.dom.com' having a Delivered-To: line
of the form:
Delivered-To: mbox-userstr-username@userhost.example.com
The ISP can make the 'mbox-userstr-' prefix anything they choose
but a string matching the user host name is likely. By using the
option 'envelope Delivered-To:' you can make fetchmail reliably
identify the original envelope recipient, but you have to strip
the 'mbox-userstr-' prefix to deliver to the correct user. This
is what this option is for.
--configdump
Parse the ~/.fetchmailrc file, interpret any command-line options
specified, and dump a configuration report to standard output.
The configuration report is a data structure assignment in the
language Python. This option is meant to be used with an
interactive ~/.fetchmailrc editor like fetchmailconf, written in
Python.
-y | --yydebug
Enables parser debugging, this option is meant to be used by
developers only.
Removed Options
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-T | --netsec
Removed before version 6.3.0, the required underlying inet6_apps
library had been discontinued and is no longer available.
USER AUTHENTICATION AND ENCRYPTION
All modes except ETRN require authentication of the client to the
server. Normal user authentication in fetchmail is very much like the
authentication mechanism of ftp(1). The correct user-id and password
depend upon the underlying security system at the mail server.
If the mail server is a Unix machine on which you have an ordinary
user account, your regular login name and password are used with
fetchmail. If you use the same login name on both the server and the
client machines, you needn't worry about specifying a user-id with the
-u option -- the default behavior is to use your login name on the
client machine as the user-id on the server machine. If you use a
different login name on the server machine, specify that login name
with the -u option. E.g., if your login name is 'jsmith' on a machine
named 'mailgrunt', you would start fetchmail as follows:
fetchmail -u jsmith mailgrunt
The default behavior of fetchmail is to prompt you for your mail
server password before the connection is established. This is the
safest way to use fetchmail and ensures that your password will not be
compromised. You may also specify your password in your
~/.fetchmailrc file. This is convenient when using fetchmail in
daemon mode or with scripts.
Using netrc files
If you do not specify a password, and fetchmail cannot extract one
from your ~/.fetchmailrc file, it will look for a ~/.netrc file in
your home directory before requesting one interactively; if an entry
matching the mail server is found in that file, the password will be
used. Fetchmail first looks for a match on poll name; if it finds
none, it checks for a match on via name. To show a practical example,
a .netrc might look like this:
machine hermes.example.org
login joe
password topsecret
You can repeat this block with different user information if you need
to provide more than one password.
This feature may allow you to avoid duplicating password information
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in more than one file.
The netrc file contains login information originally set for ftp(1)
but fetchmail understands typical constructs of this file to use it
for passwords. The syntax consists of tokens (usually in pairs with
strings). Strings can be quoted with single or double quotes, as in
"quoted string", to allow enclosing blanks, and a backslash (\) within
a quoted string will escape the following character, so that a
password can contain quote marks themselves. Tokens are separated by
spaces, tabs or newline characters.
These tokens are understood:
machine name
Identify a remote computer name for which the following tokens
apply. It needs to match either fetchmail's poll or via name.
login name
Defines the user name that fetchmail would match when looking for
entries. Fetchmail ignores zero-length names or entries without
login.
password string
Defines the password that fetchmail will use when machine and
login match the poll/via name and the username.
default
This is like machine, but would match any name. Fetchmail ignores
it. After this, no more machine sections are permitted.
account string
Fetchmail ignores this token/string pair.
macdef macro_name
Fetchmail ignores this macro definition, meaning this, the
remainder of the lines, and all following lines until a blank
line is found (i. e., two consecutive new-line characters). Then
.netrc parsing resumes.
On mail servers that do not provide ordinary user accounts, your
user-id and password are usually assigned by the server administrator
when you apply for a mailbox on the server. Contact your server
administrator if you do not know the correct user-id and password for
your mailbox account.
Secure Socket Layers (SSL) and Transport
All retrieval protocols can use SSL or TLS wrapping for the transport.
Additionally, POP3 and IMAP retrieval can also negotiate SSL/TLS by
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means of STARTTLS (or STLS).
You can access TLS-encrypted services by specifying the options
starting with --ssl, such as --ssl, --sslproto, --nosslcertck, and
others. You can also do this using the corresponding user options in
the .fetchmailrc file. Some services, such as POP3 and IMAP, have
different well known ports defined for the SSL encrypted services.
The encrypted ports will be selected automatically when SSL is enabled
and no explicit port is specified. Also, the --sslcertck command
line or sslcertck run control file option should be used at least in
documentation to force strict certificate checking with older
fetchmail versions - see below.
If TLS or SSL is not configured, fetchmail will usually still try to
use STARTTLS. In practice, TLS or SSL it still mandatory because
--sslcertck is a default setting and implicitly requires STARTTLS.
STARTTLS can be enforced by using --sslproto~auto and defeated by
using --sslproto~''. STARTTLS connections use the same port as the
unencrypted version of the protocol and negotiate TLS via special
command. The --sslcertck command line or sslcertck run control file
option should be used to force strict certificate checking - see
below.
--sslcertck is recommended: When connecting to an SSL or TLS encrypted
server, the server presents a certificate to the client for
validation. The certificate is checked to verify that the common name
in the certificate matches the name of the server being contacted and
that the effective and expiration dates in the certificate indicate
that it is currently valid. If any of these checks fail, a warning
message is printed, but the connection continues. The server
certificate does not need to be signed by any specific Certifying
Authority and may be a "self-signed" certificate. If the --sslcertck
command line option or sslcertck run control file option is used,
fetchmail will instead abort if any of these checks fail, because it
must assume that there is a man-in-the-middle attack in this scenario,
hence fetchmail must not expose clear-text passwords. Use of the
sslcertck or --sslcertck option is therefore advised; it has become
the default in fetchmail 6.4.0.
Some SSL encrypted servers may request a client side certificate. A
client side public SSL certificate and private SSL key may be
specified. If requested by the server, the client certificate is sent
to the server for validation. Some servers may require a valid client
certificate and may refuse connections if a certificate is not
provided or if the certificate is not valid. Some servers may require
client side certificates be signed by a recognized Certifying
Authority. The format for the key files and the certificate files is
that required by the underlying SSL libraries (OpenSSL in the general
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case).
A word of care about the use of SSL: While above mentioned setup with
self-signed server certificates retrieved over the wires can protect
you from a passive eavesdropper, it does not help against an active
attacker. It is clearly an improvement over sending the passwords in
clear, but you should be aware that a man-in-the-middle attack is
trivially possible (in particular with tools such as dsniff Use of
strict certificate checking with a certification authority recognized
by server and client, or perhaps of an SSH tunnel (see below for some
examples) is preferable if you care seriously about the security of
your mailbox and passwords.
POP3 VARIANTS
Early versions of POP3 (RFC1081, RFC1225) supported a crude form of
independent authentication using the .rhosts file on the mail server
side. Under this RPOP variant, a fixed per-user ID equivalent to a
password was sent in clear over a link to a reserved port, with the
command RPOP rather than PASS to alert the server that it should do
special checking. RPOP is supported by fetchmail (you can specify
'protocol RPOP' to have the program send 'RPOP' rather than 'PASS')
but its use is strongly discouraged, and support will be removed from
a future fetchmail version. This facility was vulnerable to spoofing
and was withdrawn in RFC1460.
RFC1460 introduced APOP authentication. In this variant of POP3, you
register an APOP password on your server host (on some servers, the
program to do this is called popauth(8)). You put the same password
in your ~/.fetchmailrc file. Each time fetchmail logs in, it sends an
MD5 hash of your password and the server greeting time to the server,
which can verify it by checking its authorization database.
Note that APOP is no longer considered resistant against man-in-the-
middle attacks.
RETR or TOP
fetchmail makes some efforts to make the server believe messages had
not been retrieved, by using the TOP command with a large number of
lines when possible. TOP is a command that retrieves the full header
and a fetchmail-specified amount of body lines. It is optional and
therefore not implemented by all servers, and some are known to
implement it improperly. On many servers however, the RETR command
which retrieves the full message with header and body, sets the "seen"
flag (for instance, in a web interface), whereas the TOP command does
not do that.
fetchmail will always use the RETR command if "fetchall" is set.
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fetchmail will also use the RETR command if "keep" is set and "uidl"
is unset. Finally, fetchmail will use the RETR command on Maillennium
POP3/PROXY servers (used by Comcast) to avoid a deliberate TOP
misinterpretation in this server that causes message corruption.
In all other cases, fetchmail will use the TOP command. This implies
that in "keep" setups, "uidl" must be set if "TOP" is desired.
Note that this description is true for the current version of
fetchmail, but the behavior may change in future versions. In
particular, fetchmail may prefer the RETR command because the TOP
command causes much grief on some servers and is only optional.
ALTERNATE AUTHENTICATION FORMS/METHODS
If your fetchmail was built with Kerberos support and you specify
Kerberos authentication (either with --auth or the .fetchmailrc option
authenticate kerberos_v4) it will try to get a Kerberos ticket from
the mail server at the start of each query. Note: if either the
pollname or via name is 'hesiod', fetchmail will try to use Hesiod to
look up the mail server.
If you use POP3 or IMAP with GSSAPI authentication, fetchmail will
expect the server to have RFC1731- or RFC1734-conforming GSSAPI
capability, and will use it. Currently this has only been tested over
Kerberos 5, so you are expected to already have a ticket-granting
ticket. You may pass a username different from your principal name
using the standard --user command or by the .fetchmailrc option user.
If your IMAP daemon returns the PREAUTH response in its greeting line,
fetchmail will notice this and skip the normal authentication step.
This can be useful, e.g., if you start imapd explicitly using ssh. In
this case you can declare the authentication value 'implicit' on that
site entry to stop .fetchmail from asking you for a password when it
starts up.
If you use client authentication with TLS1 and your IMAP daemon
returns the AUTH=EXTERNAL response, fetchmail will notice this and
will use the authentication shortcut and will not send the passphrase.
In this case you can declare the authentication value 'external'
on that site to stop fetchmail from asking you for a password when it
starts up.
If you are using POP3, and the server issues a one-time-password
challenge conforming to RFC1938, fetchmail will use your password as a
pass phrase to generate the required response. This avoids sending
secrets over the net unencrypted.
Compuserve's RPA authentication is supported. If you compile in the
support, fetchmail will try to perform an RPA pass-phrase
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authentication instead of sending over the password unencrypted if it
detects "@compuserve.com" in the host name.
If you are using IMAP, Microsoft's NTLM authentication (used by
Microsoft Exchange) is supported. If you compile in the support,
fetchmail will try to perform an NTLM authentication (instead of
sending over the password unencrypted) whenever the server returns
AUTH=NTLM in its capability response. Specify a user option value that
looks like 'user@domain': the part to the left of the @ will be passed
as the username and the part to the right as the NTLM domain.
ESMTP AUTH
fetchmail also supports authentication to the ESMTP server on the
client side according to RFC 2554. You can specify a name/password
pair to be used with the keywords 'esmtpname' and 'esmtppassword'; the
former defaults to the username of the calling user.
DAEMON MODE
Introducing the daemon mode
In daemon mode, fetchmail puts itself into the background and runs
forever, querying each specified host and then sleeping for a given
polling interval.
Starting the daemon mode
There are several ways to make fetchmail work in daemon mode. On the
command line, --daemon <interval> or -d <interval> option runs
fetchmail in daemon mode. You must specify a numeric argument which
is a polling interval (time to wait after completing a whole poll
cycle with the last server and before starting the next poll cycle
with the first server) in seconds.
Example: simply invoking
fetchmail -d 900
will, therefore, poll all the hosts described in your ~/.fetchmailrc
file (except those explicitly excluded with the 'skip' verb) a bit
less often than once every 15 minutes (exactly: 15 minutes + time that
the poll takes).
It is also possible to set a polling interval in your ~/.fetchmailrc
file by saying 'set daemon <interval>', where <interval> is an integer
number of seconds. If you do this, fetchmail will always start in
daemon mode unless you override it with the command-line option
--daemon 0 or -d0.
Only one daemon process is permitted per user; in daemon mode,
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fetchmail sets up a per-user lock file to guarantee this. (You can
however cheat and set the FETCHMAILHOME environment variable to
overcome this setting, but in that case, it is your responsibility to
make sure you are not polling the same server with two processes at
the same time.)
Awakening the background daemon
Normally, calling fetchmail with a daemon in the background sends a
wake-up signal to the daemon and quits without output. The background
daemon then starts its next poll cycle immediately. The wake-up
signal, SIGUSR1, can also be sent manually. The wake-up action also
clears any 'wedged' flags indicating that connections have wedged due
to failed authentication or multiple timeouts.
Terminating the background daemon
The option -q or --quit will kill a running daemon process instead of
waking it up (if there is no such process, fetchmail will notify you).
If the --quit option appears last on the command line, fetchmail will
kill the running daemon process and then quit. Otherwise, fetchmail
will first kill a running daemon process and then continue running
with the other options.
Useful options for daemon mode
The -L <filename> or --logfile <filename> option (keyword: set
logfile) is only effective when fetchmail is detached and in daemon
mode. Note that the logfile must exist before fetchmail is run, you
can use the touch(1) command with the filename as its sole argument to
create it.
This option allows you to redirect status messages into a specified
logfile (follow the option with the logfile name). The logfile is
opened for append, so previous messages are not deleted. This is
primarily useful for debugging configurations. Note that fetchmail
does not detect if the logfile is rotated, the logfile is only opened
once when fetchmail starts. You need to restart fetchmail after
rotating the logfile and before compressing it (if applicable).
Since v6.5.0, the log file is prefixed with time stamps, in local time
and in the format "Jun 20 23:45:01 fetchmail: ". It will be localized
through the environment variables LC_TIME (or LC_ALL) and TZ.
The --syslog option (keyword: set syslog) allows you to redirect
status and error messages emitted to the syslog(3) system daemon if
available. Messages are logged with an id of fetchmail, the facility
LOG_MAIL, and priorities LOG_ERR, LOG_ALERT or LOG_INFO. This option
is intended for logging status and error messages which indicate the
status of the daemon and the results while fetching mail from the
server(s). Error messages for command line options and parsing the
.fetchmailrc file are still written to stderr, or to the specified log
file. The --nosyslog option turns off use of syslog(3), assuming it
is turned on in the ~/.fetchmailrc file. This option is overridden,
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in certain situations, by --logfile (which see).
The -N or --nodetach option suppresses backgrounding and detachment of
the daemon process from its control terminal. This is useful for
debugging or when fetchmail runs as the child of a supervisor process
such as init(8) or Gerrit Pape's runit(8). Note that this also causes
the logfile option to be ignored.
Note that while running in daemon mode polling a POP2 or IMAP2bis
server, transient errors (such as DNS failures or sendmail delivery
refusals) may force the fetchall option on for the duration of the
next polling cycle. This is a robustness feature. It means that if a
message is fetched (and thus marked seen by the mail server) but not
delivered locally due to some transient error, it will be re-fetched
during the next poll cycle. (The IMAP logic does not delete messages
until they are delivered, so this problem does not arise.)
If you touch or change the ~/.fetchmailrc file while fetchmail is
running in daemon mode, this will be detected at the beginning of the
next poll cycle. When a changed ~/.fetchmailrc is detected, fetchmail
rereads it and restarts from scratch (using exec(2); no state
information is retained in the new instance). Note that if fetchmail
needs to query for passwords, of that if you break the ~/.fetchmailrc
file's syntax, the new instance will softly and silently vanish away
on startup.
ADMINISTRATIVE OPTIONS
The --postmaster <name> option (keyword: set postmaster) specifies the
last-resort username to which multidrop mail is to be forwarded if no
matching local recipient can be found. It is also used as destination
of undeliverable mail if the 'bouncemail' global option is off and
additionally for spam-blocked mail if the 'bouncemail' global option
is off and the 'spambounce' global option is on. This option defaults
to the user who invoked fetchmail. If the invoking user is root, then
the default of this option is the user 'postmaster'. Setting
postmaster to the empty string causes such mail as described above to
be discarded - this however is usually a bad idea. See also the
description of the 'FETCHMAILUSER' environment variable in the
ENVIRONMENT section below.
The --nobounce behaves like the "set no bouncemail" global option,
which see.
The --invisible option (keyword: set invisible) tries to make
fetchmail invisible. Normally, fetchmail behaves like any other MTA
would -- it generates a Received header into each message describing
its place in the chain of transmission, and tells the MTA it forwards
to that the mail came from the machine fetchmail itself is running on.
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If the invisible option is on, the Received header is suppressed and
fetchmail tries to spoof the MTA it forwards to into thinking it came
directly from the mail server host.
The --showdots option (keyword: set showdots) forces fetchmail to show
progress dots even if the output goes to a file or fetchmail is not in
verbose mode. Fetchmail shows the dots by default when run in
--verbose mode and output goes to console. This option is ignored in
--silent mode.
By specifying the --tracepolls option, you can ask fetchmail to add
information to the Received header on the form "polling {label}
account {user}", where {label} is the account label (from the
specified rcfile, normally ~/.fetchmailrc) and {user} is the username
which is used to log on to the mail server. This header can be used to
make filtering email where no useful header information is available
and you want mail from different accounts sorted into different
mailboxes (this could, for example, occur if you have an account on
the same server running a mailing list, and are subscribed to the list
using that account). The default is not adding any such header. In
.fetchmailrc, this is called 'tracepolls'.
RETRIEVAL FAILURE MODES
The protocols fetchmail uses to talk to mail servers are next to
bulletproof. In normal operation forwarding to port 25, no message is
ever deleted (or even marked for deletion) on the host until the SMTP
listener on the client side has acknowledged to fetchmail that the
message has been either accepted for delivery or rejected due to a
spam block.
When forwarding to an MDA, however, there is more possibility of
error. Some MDAs are 'safe' and reliably return a nonzero status on
any delivery error, even one due to temporary resource limits. The
maildrop(1) program is like this; so are most programs designed as
mail transport agents, such as sendmail(1), including the sendmail
wrapper of Postfix and exim(1). These programs give back a reliable
positive acknowledgement and can be used with the mda option with no
risk of mail loss. Unsafe MDAs, though, may return 0 even on delivery
failure. If this happens, you will lose mail.
The normal mode of fetchmail is to try to download only 'new'
messages, leaving untouched (and undeleted) messages you have already
read directly on the server (or fetched with a previous fetchmail
--keep). But you may find that messages you have already read on the
server are being fetched (and deleted) even when you do not specify
--all. There are several reasons this can happen.
One could be that you are using POP2. The POP2 protocol includes no
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representation of 'new' or 'old' state in messages, so fetchmail must
treat all messages as new all the time. But POP2 is obsolete, so this
is unlikely.
A potential POP3 problem might be servers that insert messages in the
middle of mailboxes (some VMS implementations of mail are rumored to
do this). The fetchmail code assumes that new messages are appended
to the end of the mailbox; when this is not true it may treat some old
messages as new and vice versa. Using UIDL whilst setting fastuidl 0
might fix this, otherwise, consider switching to IMAP.
Yet another POP3 problem is that if they cannot make temporary files
in the user's home directory, some POP3 servers will hand back an
undocumented response that causes fetchmail to spuriously report "No
mail".
The IMAP code uses the presence or absence of the server flag \Seen to
decide whether or not a message is new. This is not the right thing
to do, fetchmail should check the UIDVALIDITY and use UID, but it does
not do that yet. Under Unix, it counts on your IMAP server to notice
the BSD-style Status flags set by mail user agents and set the \Seen
flag from them when appropriate. All Unix IMAP servers we know of do
this, though it is not specified by the IMAP RFCs. If you ever trip
over a server that does not, the symptom will be that messages you
have already read on your host will look new to the server. In this
(unlikely) case, only messages you fetched with fetchmail --keep will
be both undeleted and marked old.
In ETRN and ODMR modes, fetchmail does not actually retrieve messages;
instead, it asks the server's SMTP listener to start a queue flush to
the client via SMTP. Therefore it sends only undelivered messages.
SPAM FILTERING
Many SMTP listeners allow administrators to set up 'spam filters' that
block unsolicited email from specified domains. A MAIL FROM or DATA
line that triggers this feature will elicit an SMTP response which
(unfortunately) varies according to the listener.
Newer versions of sendmail return an error code of 571.
According to RFC2821, the correct thing to return in this situation is
550 "Requested action not taken: mailbox unavailable" (the draft adds
"[E.g., mailbox not found, no access, or command rejected for policy
reasons].").
Older versions of the exim MTA return 501 "Syntax error in parameters
or arguments".
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The postfix MTA runs 554 as an antispam response.
Zmailer may reject code with a 500 response (followed by an enhanced
status code that contains more information).
Return codes which fetchmail treats as antispam responses and discards
the message can be set with the 'antispam' option. This is one of the
only three circumstance under which fetchmail ever discards mail (the
others are the 552 and 553 errors described below, and the suppression
of multi-dropped messages with a message-ID already seen).
If fetchmail is fetching from an IMAP server, the antispam response
will be detected and the message rejected immediately after the
headers have been fetched, without reading the message body. Thus,
you will not pay for downloading spam message bodies.
By default, the list of antispam responses is empty.
If the spambounce global option is on, mail that is spam-blocked
triggers an RFC1892/RFC1894 bounce message informing the originator
that we do not accept mail from it. See also BUGS.
SMTP/ESMTP ERROR HANDLING
Besides the spam-blocking described above, fetchmail takes special
actions - that may be modified by the --softbounce option - on the
following SMTP/ESMTP error response codes
452 (insufficient system storage)
Leave the message in the server mailbox for later retrieval.
552 (message exceeds fixed maximum message size)
Delete the message from the server. Send bounce-mail to the
originator.
553 (invalid sending domain)
Delete the message from the server. Do not even try to send
bounce-mail to the originator.
Other errors greater or equal to 500 trigger bounce mail back to the
originator, unless suppressed by --softbounce. See also BUGS.
THE RUN CONTROL FILE
The preferred way to set up fetchmail is to write a .fetchmailrc file
in your home directory (you may do this directly, with a text editor,
or indirectly via fetchmailconf). When there is a conflict between
the command-line arguments and the arguments in this file, the
command-line arguments take precedence.
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To protect the security of your passwords, your ~/.fetchmailrc may not
normally have more than 0700 (u=rwx,g=,o=) permissions; fetchmail will
complain and exit otherwise (this check is suppressed when --version
is on).
You may read the .fetchmailrc file as a list of commands to be
executed when fetchmail is called with no arguments.
Run Control Syntax
Comments begin with a '#' and extend through the end of the line.
Otherwise the file consists of a series of server entries or global
option statements in a free-format, token-oriented syntax.
There are four kinds of tokens: grammar keywords, numbers (i.e.,
decimal digit sequences), unquoted strings, and quoted strings. A
quoted string is bounded by double quotes and may contain whitespace
(and quoted digits are treated as a string). Note that quoted strings
will also contain line feed characters if they run across two or more
lines, unless you use a backslash to join lines (see below). An
unquoted string is any whitespace-delimited token that is neither
numeric, string quoted nor contains the special characters ',', ';',
':', or '='.
Any amount of whitespace separates tokens in server entries, but is
otherwise ignored. You may use backslash escape sequences (\n for LF,
\t for HT, \b for BS, \r for CR, \nnn for decimal (where nnn cannot
start with a 0), \0ooo for octal, and \xhh for hex) to embed non-
printable characters or string delimiters in strings. In quoted
strings, a backslash at the very end of a line will cause the
backslash itself and the line feed (LF or NL, new line) character to
be ignored, so that you can wrap long strings. Without the backslash
at the line end, the line feed character would become part of the
string.
Warning: while these resemble C-style escape sequences, they are not
the same. fetchmail only supports these eight styles. C supports more
escape sequences that consist of backslash (\) and a single character,
but does not support decimal codes and does not require the leading 0
in octal notation. Example: fetchmail interprets \233 the same as
\xE9 (Latin small letter e with acute), where C would interpret \233
as octal 0233 = \x9B (CSI, control sequence introducer).
Each server entry consists of one of the keywords 'poll' or 'skip',
followed by a server name, followed by server options, followed by any
number of user (or username) descriptions, followed by user options.
Note: the most common cause of syntax errors is mixing up user and
server options or putting user options before the user descriptions.
For backward compatibility, the word 'server' is a synonym for 'poll'.
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You can use the noise keywords 'and', 'with', 'has', 'wants', and
'options' anywhere in an entry to make it resemble English. They are
ignored, but can make entries much easier to read at a glance. The
punctuation characters ':', ';' and ',' are also ignored.
Poll versus Skip
The 'poll' verb tells fetchmail to query this host when it is run with
no arguments. The 'skip' verb tells fetchmail not to poll this host
unless it is explicitly named on the command line. (The 'skip' verb
allows you to experiment with test entries safely, or easily disable
entries for hosts that are temporarily down.)
KEYWORD/OPTION SUMMARY
Here are the legal options. Keyword suffixes enclosed in square
brackets are optional. Those corresponding to short command-line
options are followed by '-' and the appropriate option letter. If
option is only relevant to a single mode of operation, it is noted as
's' or 'm' for singledrop- or multidrop-mode, respectively.
Here are the legal global options:
l l l lw34. Keyword Opt Mode Function _ set daemon
-d T{ Set a background poll interval in seconds. T} set
postmaster T{ Give the name of the last-resort mail
recipient (default: user running fetchmail, "postmaster" if run by the
root user) T} set bouncemail T{ Direct error mail to
the sender (default) T} set no bouncemail T{ Direct error
mail to the local postmaster (as per the 'postmaster' global option
above). T} set no spambounce T{ Do not bounce spam-
blocked mail (default). T} set spambounce T{ Bounce
blocked spam-blocked mail (as per the 'antispam' user option) back to
the destination as indicated by the 'bouncemail' global option.
Warning: Do not use this to bounce spam back to the sender - most spam
is sent with false sender address and thus this option hurts innocent
bystanders. T} set no softbounce T{ Delete permanently
undeliverable mail. It is recommended to use this option if the
configuration has been thoroughly tested. T} set
softbounce T{ Keep permanently undeliverable mail as
though a temporary error had occurred (default). T} set logfile
-L T{ Name of a file to append error and status messages to.
Only effective in daemon mode and if fetchmail detaches. If
effective, overrides set syslog. T} set pidfile -p T{ Name
of the PID file. T} set idfile -i T{ Name of the file to
store UID lists in. T} set syslog T{ Do error logging
through syslog(3). May be overridden by set logfile. T} set no syslog
T{ Turn off error logging through syslog(3). (default)
T} set properties T{ String value that is ignored by
fetchmail (may be used by extension scripts). T}
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Here are the legal server options:
l l l lw34. Keyword Opt Mode Function _ via T{
Specify DNS name of mail server, overriding poll name T}
proto[col] -p T{ Specify protocol (case insensitive): POP2,
POP3, IMAP, APOP, KPOP T} local[domains] m T{ Specify
domain(s) to be regarded as local T} port T{ Specify
TCP/IP service port (obsolete, use 'service' instead). T} service
-P T{ Specify service name (a numeric value is also allowed
and considered a TCP/IP port number). T} auth[enticate] T{
Set authentication type (default 'any') T} timeout -t T{
Server inactivity timeout in seconds (default 300) T}
envelope -E m T{ Specify envelope-address header name T} no
envelope m T{ Disable looking for envelope address T}
qvirtual -Q m T{ Qmail virtual domain prefix to remove from user
name T} aka m T{ Specify alternate DNS names of mail
server T} interface -I T{ specify IP interface(s) that must be
up for server poll to take place T} monitor -M T{
Specify IP address to monitor for activity T} plugin T{
Specify command through which to make server connections. T} plugout
T{ Specify command through which to make listener
connections. T} dns m T{ Enable DNS lookup for
multidrop (default) T} no dns m T{ Disable DNS lookup for
multidrop T} checkalias m T{ Do comparison by IP address
for multidrop T} no checkalias m T{ Do comparison by name for
multidrop (default) T} uidl -U T{ Force POP3 to use
client-side UIDLs (recommended) T} no uidl T{ Turn
off POP3 use of client-side UIDLs (default) T} interval
T{ Only check this site every N poll cycles; N is a
numeric argument. T} tracepolls T{ Add poll tracing
information to the Received header T} principal T{ Set
Kerberos principal (only useful with IMAP and kerberos) T} esmtpname
T{ Set name for RFC2554 authentication to the ESMTP
server. T} esmtppassword T{ Set password for RFC2554
authentication to the ESMTP server. T} bad-header T{
How to treat messages with a bad header. Can be reject (default) or
accept. T} idletimeout T{ Idle waiting timeout (in
seconds), see --idle. T}
Here are the legal user descriptions and options:
l l l lw34. Keyword Opt Mode Function _
user[name] -u T{ This is the user description and must come
first after server description and after possible server options, and
before user options.
It sets the remote user name if by itself or followed by 'there', or
the local user name if followed by 'here'. T} is T{
Connect local and remote user names T} to T{ Connect
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local and remote user names T} pass[word] T{ Specify
remote account password T} ssl T{ Connect to server
over the specified base protocol using SSL encryption T} sslcert
T{ Specify file for client side public SSL certificate T}
sslcertck T{ Enable strict certificate checking and abort
connection on failure. Default only since fetchmail v6.4.0. T} no
sslcertck T{ Disable strict certificate checking and
permit connections to continue on failed verification. Discouraged.
Should only be used together with sslfingerprint. T}
sslcertfile T{ Specify file with trusted CA certificates
T} sslcertpath T{ Specify c_rehash-ed directory with
trusted CA certificates. T} sslfingerprint T{ Specify the
expected server certificate finger print from an MD5 hash. Fetchmail
will disconnect and log an error if it does not match. T} sslkey
T{ Specify file for client side private SSL key T}
sslproto T{ Force ssl protocol for connection T} folder
-r T{ Specify remote folder to query T}
smtphost -S T{ Specify smtp host(s) to forward to T}
fetchdomains m T{ Specify domains for which mail should be
fetched T} smtpaddress -D T{ Specify the domain to be put in
RCPT TO lines T} smtpname T{ Specify the user and domain to
be put in RCPT TO lines T} antispam -Z T{ Specify what SMTP
returns are interpreted as spam-policy blocks T} mda
-m T{ Specify MDA for local delivery T} bsmtp
T{ Specify BSMTP batch file to append to T}
preconnect T{ Command to be executed before each
connection T} postconnect T{ Command to be executed after
each connection T} keep -k T{ Do not delete seen messages
from server (for POP3, uidl is recommended) T} flush -F T{
Flush all seen messages before querying (DANGEROUS) T} limitflush
T{ Flush all oversized messages before querying T}
fetchall -a T{ Fetch all messages whether seen or not T}
rewrite T{ Rewrite destination addresses for reply
(default) T} stripcr T{ Strip carriage returns from ends
of lines T} forcecr T{ Force carriage returns at ends of
lines T} pass8bits T{ Force BODY=8BITMIME to ESMTP listener
T} dropstatus T{ Strip Status and X-Mozilla-Status lines
out of incoming mail T} dropdelivered T{ Strip Delivered-To
lines out of incoming mail T} mimedecode T{ Convert
quoted-printable to 8-bit in MIME messages T} idle T{
Idle waiting for new messages after each poll (IMAP only) T} forceidle
T{ Idle waiting for new messages after each poll (IMAP
only, forced) T} no keep -K T{ Delete seen messages from
server (default) T} no flush T{ Do not flush all seen
messages before querying (default) T} no fetchall T{
Retrieve only new messages (default) T} no rewrite T{ Do
not rewrite headers T} no stripcr T{ Do not strip
carriage returns (default) T} no forcecr T{ Do not force
carriage returns at EOL (default) T} no pass8bits T{ Do
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not force BODY=8BITMIME to ESMTP listener (default) T} no
dropstatus T{ Do not drop Status headers (default) T} no
dropdelivered T{ Do not drop Delivered-To headers
(default) T} no mimedecode T{ Do not convert quoted-
printable to 8-bit in MIME messages (default) T} no idle
T{ Do not idle waiting for new messages after each poll
(IMAP only) T} limit -l T{ Set message size limit T}
warnings -w T{ Set message size warning interval T}
batchlimit -b T{ Max # messages to forward in single
connect T} fetchlimit -B T{ Max # messages to fetch in
single connect T} fetchsizelimit T{ Max # message sizes to
fetch in single transaction T} fastuidl T{ Use binary
search for first unseen message (POP3 only) T} expunge -e T{
Perform an expunge on every #th message (IMAP and POP3 only) T}
properties T{ String value is ignored by fetchmail (may
be used by extension scripts) T}
All user options must begin with a user description (user or username
option) and follow all server descriptions and options.
In the .fetchmailrc file, the 'envelope' string argument may be
preceded by a whitespace-separated number. This number, if specified,
is the number of such headers to skip over (that is, an argument of 1
selects the second header of the given type). This is sometimes
useful for ignoring bogus envelope headers created by an ISP's local
delivery agent or internal forwards (through mail inspection systems,
for instance).
Keywords Not Corresponding To Option Switches
The 'folder' and 'smtphost' options (unlike their command-line
equivalents) can take a space- or comma-separated list of names
following them.
All options correspond to the obvious command-line arguments, except
the following: 'via', 'interval', 'aka', 'is', 'to', 'dns'/'no dns',
'checkalias'/'no checkalias', 'password', 'preconnect', 'postconnect',
'localdomains', 'stripcr'/'no stripcr', 'forcecr'/'no forcecr',
'pass8bits'/'no pass8bits' 'dropstatus/no dropstatus',
'dropdelivered/no dropdelivered', 'mimedecode/no mimedecode', 'no
idle', and 'no envelope'.
The 'via' option is for if you want to have more than one
configuration pointing at the same site. If it is present, the string
argument will be taken as the actual DNS name of the mail server host
to query. This will override the argument of poll, which can then
simply be a distinct label for the configuration (e.g., what you would
give on the command line to explicitly query this host).
The 'interval' option (which takes a numeric argument) allows you to
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poll a server less frequently than the basic poll interval. If you
say 'interval N' the server this option is attached to will only be
queried every N poll intervals.
Singledrop versus Multidrop options
Please ensure you read the section titled THE USE AND ABUSE OF
MULTIDROP MAILBOXES if you intend to use multidrop mode.
The 'is' or 'to' keywords associate the following local (client)
name(s) (or server-name to client-name mappings separated by =) with
the mail server user name in the entry. If an is/to list has '*' as
its last name, unrecognized names are simply passed through. Note that
until fetchmail version 6.3.4 inclusively, these lists could only
contain local parts of user names (fetchmail would only look at the
part before the @ sign). fetchmail versions 6.3.5 and newer support
full addresses on the left hand side of these mappings, and they take
precedence over any 'localdomains', 'aka', 'via' or similar mappings.
A single local name can be used to support redirecting your mail when
your username on the client machine is different from your name on the
mail server. When there is only a single local name, mail is
forwarded to that local username regardless of the message's Received,
To, Cc, and Bcc headers. In this case, fetchmail never does DNS
lookups.
When there is more than one local name (or name mapping), fetchmail
looks at the envelope header, if configured, and otherwise at the
Received, To, Cc, and Bcc headers of retrieved mail (this is
'multidrop mode'). It looks for addresses with host name parts that
match your poll name or your 'via', 'aka' or 'localdomains' options,
and usually also for host name parts which DNS tells it are aliases of
the mail server. See the discussion of 'dns', 'checkalias',
'localdomains', and 'aka' for details on how matching addresses are
handled.
If fetchmail cannot match any mail server usernames or localdomain
addresses, the mail will be bounced. Normally it will be bounced to
the sender, but if the 'bouncemail' global option is off, the mail
will go to the local postmaster instead. (see the 'postmaster' global
option). See also BUGS.
The 'dns' option (normally on) controls the way addresses from
multidrop mailboxes are checked. On, it enables logic to check each
host address that does not match an 'aka' or 'localdomains'
declaration by looking it up with DNS. When a mail server username is
recognized attached to a matching host name part, its local mapping is
added to the list of local recipients.
The 'checkalias' option (normally off) extends the lookups performed
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by the 'dns' keyword in multidrop mode, providing a way to cope with
remote MTAs that identify themselves using their canonical name, while
they are polled using an alias. When such a server is polled, checks
to extract the envelope address fail, and fetchmail reverts to
delivery using the To/Cc/Bcc headers (See below 'Header versus
Envelope addresses'). Specifying this option instructs fetchmail to
retrieve all the IP addresses associated with both the poll name and
the name used by the remote MTA and to do a comparison of the IP
addresses. This comes in handy in situations where the remote server
undergoes frequent canonical name changes, that would otherwise
require modifications to the rcfile. 'checkalias' has no effect if
'no dns' is specified in the rcfile.
The 'aka' option is for use with multidrop mailboxes. It allows you
to pre-declare a list of DNS aliases for a server. This is an
optimization hack that allows you to trade space for speed. When
fetchmail, while processing a multidrop mailbox, grovels through
message headers looking for names of the mail server, pre-declaring
common ones can save it from having to do DNS lookups. Note: the
names you give as arguments to 'aka' are matched as suffixes -- if you
specify (say) 'aka netaxs.com', this will match not just a host name
netaxs.com, but any host name that ends with '.netaxs.com'; such as
(say) pop3.netaxs.com and mail.netaxs.com.
The 'localdomains' option allows you to declare a list of domains
which fetchmail should consider local. When fetchmail is parsing
address lines in multidrop modes, and a trailing segment of a host
name matches a declared local domain, that address is passed through
to the listener or MDA unaltered (local-name mappings are not
applied).
If you are using 'localdomains', you may also need to specify 'no
envelope', which disables fetchmail's normal attempt to deduce an
envelope address from the Received line or X-Envelope-To header or
whatever header has been previously set by 'envelope'. If you set 'no
envelope' in the defaults entry it is possible to undo that in
individual entries by using 'envelope <string>'. As a special case,
'envelope "Received"' restores the default parsing of Received lines.
The password option requires a string argument, which is the password
to be used with the entry's server.
The 'preconnect' keyword allows you to specify a shell command to be
executed just before each time fetchmail establishes a mail server
connection. This may be useful if you are attempting to set up secure
POP connections with the aid of ssh(1). If the command returns a
nonzero status, the poll of that mail server will be aborted.
Similarly, the 'postconnect' keyword similarly allows you to specify a
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shell command to be executed just after each time a mail server
connection is taken down.
The 'forcecr' option controls whether lines terminated by LF only are
given CRLF termination before forwarding. Strictly speaking RFC821
requires this, but few MTAs enforce the requirement so this option is
normally off (only one such MTA, qmail, is in significant use at time
of writing).
The 'stripcr' option controls whether carriage returns are stripped
out of retrieved mail before it is forwarded. It is normally not
necessary to set this, because it defaults to 'on' (CR stripping
enabled) when there is an MDA declared but 'off' (CR stripping
disabled) when forwarding is via SMTP. If 'stripcr' and 'forcecr' are
both on, 'stripcr' will override.
The 'pass8bits' option exists to cope with Microsoft mail programs
that stupidly slap a "Content-Transfer-Encoding: 7bit" on everything.
With this option off (the default) and such a header present,
fetchmail declares BODY=7BIT to an ESMTP-capable listener; this causes
problems for messages actually using 8-bit ISO or KOI-8 character
sets, which will be garbled by having the high bits of all characters
stripped. If 'pass8bits' is on, fetchmail is forced to declare
BODY=8BITMIME to any ESMTP-capable listener. If the listener is 8-
bit-clean (as all the major ones now are) the right thing will
probably result.
The 'dropstatus' option controls whether nonempty Status and X-
Mozilla-Status lines are retained in fetched mail (the default) or
discarded. Retaining them allows your MUA to see what messages (if
any) were marked seen on the server. On the other hand, it can
confuse some new-mail notifiers, which assume that anything with a
Status line in it has been seen. (Note: the empty Status lines
inserted by some buggy POP servers are unconditionally discarded.)
The 'dropdelivered' option controls whether Delivered-To headers will
be kept in fetched mail (the default) or discarded. These headers are
added by qmail and Postfix mail servers in order to avoid mail loops
but may get in your way if you try to "mirror" a mail server within
the same domain. Use with caution.
The 'mimedecode' option controls whether MIME messages using the
quoted-printable encoding are automatically converted into pure 8-bit
data. If you are delivering mail to an ESMTP-capable, 8-bit-clean
listener (that includes all of the major MTAs like sendmail), then
this will automatically convert quoted-printable message headers and
data into 8-bit data, making it easier to understand when reading
mail. If your e-mail programs know how to deal with MIME messages,
then this option is not needed. The mimedecode option is off by
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default, because doing RFC2047 conversion on headers throws away
character-set information and can lead to bad results if the encoding
of the headers differs from the body encoding.
The 'idle' option is intended to be used with IMAP servers supporting
the RFC2177 IDLE command extension, but does not strictly require it.
If it is enabled, and fetchmail detects that IDLE is supported, an
IDLE will be issued at the end of each poll. This will tell the IMAP
server to hold the connection open and notify the client when new mail
is available. If IDLE is not supported, fetchmail will simulate it by
periodically issuing NOOP. If you need to poll a link frequently, IDLE
can save bandwidth by eliminating TCP/IP connects and LOGIN/LOGOUT
sequences. On the other hand, an IDLE connection will eat almost all
of your fetchmail's time, because it will never drop the connection
and allow other polls to occur unless the server times out the IDLE.
It also does not work with multiple folders; only the first folder
will ever be polled.
The 'properties' option is an extension mechanism. It takes a string
argument, which is ignored by fetchmail itself. The string argument
may be used to store configuration information for scripts which
require it. In particular, the output of '--configdump' option will
make properties associated with a user entry readily available to a
Python script.
Miscellaneous Run Control Options
The words 'here' and 'there' have useful English-like significance.
Normally 'user eric is esr' would mean that mail for the remote user
'eric' is to be delivered to 'esr', but you can make this clearer by
saying 'user eric there is esr here', or reverse it by saying 'user
esr here is eric there'
Legal protocol identifiers for use with the 'protocol' keyword are:
auto (or AUTO) (legacy, to be removed from future release)
pop2 (or POP2) (legacy, to be removed from future release)
pop3 (or POP3)
sdps (or SDPS)
imap (or IMAP)
apop (or APOP)
kpop (or KPOP)
Legal authentication types are 'any', 'password', 'kerberos',
'kerberos_v4', 'kerberos_v5' and 'gssapi', 'cram-md5', 'otp', 'msn'
(only for POP3), 'ntlm', 'implicit', 'external' (only IMAP). The
'password' type specifies authentication by normal transmission of a
password (the password may be plain text or subject to protocol-
specific encryption as in CRAM-MD5); 'kerberos' tells fetchmail to try
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to get a Kerberos ticket at the start of each query instead, and send
an arbitrary string as the password; and 'gssapi' tells fetchmail to
use GSSAPI authentication. See the description of the 'auth' keyword
for more.
Specifying 'kpop' sets POP3 protocol over port 1109 with Kerberos V4
authentication. These defaults may be overridden by later options.
There are some global option statements: 'set logfile' followed by a
string sets the same global specified by --logfile. A command-line
--logfile option will override this. Note that --logfile is only
effective if fetchmail detaches itself from the terminal and the
logfile already exists before fetchmail is run, and it overrides
--syslog in this case. Also, 'set daemon' sets the poll interval as
--daemon does. This can be overridden by a command-line --daemon
option; in particular --daemon~0 can be used to force foreground
operation. The 'set postmaster' statement sets the address to which
multidrop mail defaults if there are no local matches. Finally, 'set
syslog' sends log messages to syslogd(8).
DEBUGGING FETCHMAIL
Fetchmail crashing
There are various ways in that fetchmail may "crash", i. e. stop
operation suddenly and unexpectedly. A "crash" usually refers to an
error condition that the software did not handle by itself. A well-
known failure mode is the "segmentation fault" or "signal 11" or
"SIGSEGV" or just "segfault" for short. These can be caused by
hardware or by software problems. Software-induced segfaults can
usually be reproduced easily and in the same place, whereas hardware-
induced segfaults can go away if the computer is rebooted, or powered
off for a few hours, and can happen in random locations even if you
use the software the same way.
For solving hardware-induced segfaults, find the faulty component and
repair or replace it. The Sig11 FAQ may help you with details.
For solving software-induced segfaults, the developers may need a
"stack backtrace".
Enabling fetchmail core dumps
By default, fetchmail suppresses core dumps as these might contain
passwords and other sensitive information. For debugging fetchmail
crashes, obtaining a "stack backtrace" from a core dump is often the
quickest way to solve the problem, and when posting your problem on a
mailing list, the developers may ask you for a "backtrace".
1. To get useful backtraces, fetchmail needs to be installed without
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getting stripped of its compilation symbols. Unfortunately, most
binary packages that are installed are stripped, and core files from
symbol-stripped programs are worthless. So you may need to recompile
fetchmail. On many systems, you can type
file `which fetchmail`
to find out if fetchmail was symbol-stripped or not. If yours was
unstripped, fine, proceed, if it was stripped, you need to recompile
the source code first. You do not usually need to install fetchmail in
order to debug it.
2. The shell environment that starts fetchmail needs to enable core
dumps. The key is the "maximum core (file) size" that can usually be
configured with a tool named "limit" or "ulimit". See the
documentation for your shell for details. In the popular bash shell,
"ulimit -Sc unlimited" will allow the core dump.
3. You need to tell fetchmail, too, to allow core dumps. To do this,
run fetchmail with the -d0 -v options. It is often easier to also add
--nosyslog -N as well.
Finally, you need to reproduce the crash. You can just start fetchmail
from the directory where you compiled it by typing ./fetchmail, so the
complete command line will start with ./fetchmail -Nvd0 --nosyslog and
perhaps list your other options.
After the crash, run your debugger to obtain the core dump. The
debugger will often be GNU GDB, you can then type (adjust paths as
necessary) gdb ./fetchmail fetchmail.core and then, after GDB has
started up and read all its files, type backtrace full, save the
output (copy & paste will do, the backtrace will be read by a human)
and then type quit to leave gdb. Note: on some systems, the core
files have different names, they might contain a number instead of the
program name, or number and name, but it will usually have "core" as
part of their name.
INTERACTION WITH RFC 822
When trying to determine the originating address of a message,
fetchmail looks through headers in the following order:
Return-Path:
Resent-Sender: (ignored if it does not contain an @ or !)
Sender: (ignored if it does not contain an @ or !)
Resent-From:
From:
Reply-To:
Apparently-From:
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The originating address is used for logging, and to set the MAIL FROM
address when forwarding to SMTP. This order is intended to cope
gracefully with receiving mailing list messages in multidrop mode. The
intent is that if a local address does not exist, the bounce message
will not be returned blindly to the author or to the list itself, but
rather to the list manager (which is less annoying).
In multidrop mode, destination headers are processed as follows:
First, fetchmail looks for the header specified by the 'envelope'
option in order to determine the local recipient address. If the mail
is addressed to more than one recipient, the Received line will not
contain any information regarding recipient addresses.
Then fetchmail looks for the Resent-To:, Resent-Cc:, and Resent-Bcc:
lines. If they exist, they should contain the final recipients and
have precedence over their To:/Cc:/Bcc: counterparts. If the Resent-*
lines do not exist, the To:, Cc:, Bcc: and Apparently-To: lines are
looked for. (The presence of a Resent-To: is taken to imply that the
person referred by the To: address has already received the original
copy of the mail.)
CONFIGURATION EXAMPLES
Note that although there are password declarations in a good many of
the examples below, this is mainly for illustrative purposes. We
recommend stashing account/password pairs in your $HOME/.netrc file,
where they can be used not just by fetchmail but by ftp(1) and other
programs.
The basic format is:
poll SERVERNAME protocol PROTOCOL username NAME password PASSWORD
Example:
poll pop.provider.net protocol pop3 username "jsmith" password "secret1"
Or, using some abbreviations:
poll pop.provider.net proto pop3 user "jsmith" password "secret1"
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Multiple servers may be listed:
poll pop.provider.net proto pop3 user "jsmith" pass "secret1"
poll other.provider.net proto pop2 user "John.Smith" pass "My^Hat"
Here is the same version with more whitespace and some noise words:
poll pop.provider.net proto pop3
user "jsmith", with password secret1, is "jsmith" here;
poll other.provider.net proto pop2:
user "John.Smith", with password "My^Hat", is "John.Smith" here;
If you need to include whitespace in a parameter string or start the
latter with a number, enclose the string in double quotes. Thus:
poll mail.provider.net with proto pop3:
user "jsmith" there has password "4u but u cannot krak this"
is jws here and wants mda "/bin/mail"
You may have an initial server description headed by the keyword
'defaults' instead of 'poll' followed by a name. Such a record is
interpreted as defaults for all queries to use. It may be overwritten
by individual server descriptions. So, you could write:
defaults proto pop3
user "jsmith"
poll pop.provider.net
pass "secret1"
poll mail.provider.net
user "jjsmith" there has password "secret2"
It is possible to specify more than one user per server. The 'user'
keyword leads off a user description, and every user specification in
a multi-user entry must include it. Here is an example:
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poll pop.provider.net proto pop3 port 3111
user "jsmith" with pass "secret1" is "smith" here
user jones with pass "secret2" is "jjones" here keep
This associates the local username 'smith' with the pop.provider.net
username 'jsmith' and the local username 'jjones' with the
pop.provider.net username 'jones'. Mail for 'jones' is kept on the
server after download.
Here is what a simple retrieval configuration for a multidrop mailbox
looks like:
poll pop.provider.net:
user maildrop with pass secret1 to golux 'hurkle'='happy' snark here
This says that the mailbox of account 'maildrop' on the server is a
multidrop box, and that messages in it should be parsed for the server
user names 'golux', 'hurkle', and 'snark'. It further specifies that
'golux' and 'snark' have the same name on the client as on the server,
but mail for server user 'hurkle' should be delivered to client user
'happy'.
Note that fetchmail, until version 6.3.4, did NOT allow full
user@domain specifications here, these would never match. Fetchmail
6.3.5 and newer support user@domain specifications on the left-hand
side of a user mapping.
Here is an example of another kind of multidrop connection:
poll pop.provider.net localdomains loonytoons.org toons.org
envelope X-Envelope-To
user maildrop with pass secret1 to * here
This also says that the mailbox of account 'maildrop' on the server is
a multidrop box. It tells fetchmail that any address in the
loonytoons.org or toons.org domains (including sub-domain addresses
like 'joe@daffy.loonytoons.org') should be passed through to the local
SMTP listener without modification. Be careful of mail loops if you
do this!
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Here is an example configuration using ssh and the plugin option. The
queries are made directly on the stdin and stdout of imapd via ssh.
Note that in this setup, IMAP authentication can be skipped.
poll mailhost.net with proto imap:
plugin "ssh %h /usr/sbin/imapd" auth implicit;
user esr is esr here
THE USE AND ABUSE OF MULTIDROP
Use the multiple-local-recipients feature with caution -- it can bite.
All multidrop features are ineffective in ETRN and ODMR modes.
Also, note that in multidrop mode duplicate mails may be suppressed.
A piece of mail is considered duplicate if it does not have a
discernible envelope recipient address, has the same header as the
message immediately preceding and more than one addressee. Such runs
of messages may be generated when copies of a message addressed to
multiple users are delivered to a multidrop box. (To be precise,
fetchmail 6.2.5 through 6.4.X use an MD5 hash of the raw message
header, and only fetchmail 6.4.16+ document this properly. Fetchmail
5.0.8 (1999-09-14) through 6.2.4 used only the Message-ID header.
5.0.7 and older did not suppress duplicates.)
Note that this duplication killer code checking the entire header is
very restrictive and may not suppress many duplicates in practice -
for instance, if some X-Original-To or Delivered-To header differs.
This is intentional and correct in such situations: wherever envelope
information is available, it should be used for reliable delivery of
mailing list and blind carbon copy (Bcc) messages. See the subsection
Duplicate suppression below for suggestions.
Header versus Envelope addresses
The fundamental problem is that by having your mail server toss
several peoples' mail in a single maildrop box, you may have thrown
away potentially vital information about who each piece of mail was
actually addressed to (the 'envelope address', as opposed to the
header addresses in the RFC822 To/Cc headers - the Bcc is not
available at the receiving end). This 'envelope address' is the
address you need in order to reroute mail properly.
Sometimes fetchmail can deduce the envelope address. If the mail
server MTA is sendmail and the item of mail had just one recipient,
the MTA will have written a 'by/for' clause that gives the envelope
addressee into its Received header. But this does not work reliably
for other MTAs, nor if there is more than one recipient. By default,
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fetchmail looks for envelope addresses in these lines; you can restore
this default with -E "Received" or 'envelope Received'.
As a better alternative, some SMTP listeners and/or mail servers
insert a header in each message containing a copy of the envelope
addresses. This header (when it exists) is often 'X-Original-To',
'Delivered-To' or 'X-Envelope-To'. Fetchmail's assumption about this
can be changed with the -E or 'envelope' option. Note that writing an
envelope header of this kind exposes the names of recipients
(including blind-copy recipients) to all receivers of the messages, so
the upstream must store one copy of the message per recipient to avoid
becoming a privacy problem.
Postfix, since version 2.0, writes an X-Original-To: header which
contains a copy of the envelope as it was received.
Qmail and Postfix generally write a 'Delivered-To' header upon
delivering the message to the mail spool and use it to avoid mail
loops. Qmail virtual domains however will prefix the user name with a
string that normally matches the user's domain. To remove this prefix
you can use the -Q or 'qvirtual' option.
Sometimes, unfortunately, neither of these methods works. That is the
point when you should contact your ISP and ask them to provide such an
envelope header, and you should not use multidrop in this situation.
When they all fail, fetchmail must fall back on the contents of To/Cc
headers (Bcc headers are not available - see below) to try to
determine recipient addressees -- and these are unreliable. In
particular, mailing-list software often ships mail with only the list
broadcast address in the To: header.
Note that a future version of fetchmail may remove To/Cc parsing!
When fetchmail cannot deduce a recipient address that is local, and
the intended recipient address was anyone other than fetchmail's
invoking user, mail will get lost. This is what makes the multidrop
feature risky without proper envelope information.
A related problem is that when you blind-copy a mail message, the Bcc
information is carried only as envelope address (it is removed from
the headers by the sending mail server, so fetchmail can see it only
if there is an X-Envelope-To header). Thus, blind-copying to someone
who gets mail over a fetchmail multidrop link will fail unless the
mail server host routinely writes X-Envelope-To or an equivalent
header into messages in your maildrop.
In conclusion, mailing lists and Bcc'd mail can only work if the
server you are fetching from
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(1) stores one copy of the message per recipient in your domain and
(2) records the envelope information in a special header
(X-Original-To, Delivered-To, X-Envelope-To).
Good Ways To Use Multidrop Mailboxes
Multiple local names can be used to administer a mailing list from the
client side of a fetchmail collection. Suppose your name is 'esr',
and you want to both pick up your own mail and maintain a mailing list
called (say) "fetchmail-friends", and you want to keep the alias list
on your client machine.
On your server, you can alias 'fetchmail-friends' to 'esr'; then, in
your .fetchmailrc, declare 'to esr fetchmail-friends here'. Then,
when mail including 'fetchmail-friends' as a local address gets
fetched, the list name will be appended to the list of recipients your
SMTP listener sees. Therefore it will undergo alias expansion
locally. Be sure to include 'esr' in the local alias expansion of
fetchmail-friends, or you will never see mail sent only to the list.
Also be sure that your listener has the "me-too" option set
(sendmail's -oXm command-line option or OXm declaration) so your name
is not removed from alias expansions in messages you send.
This trick is not without its problems, however. You will begin to
see this when a message comes in that is addressed only to a mailing
list you do not have declared as a local name. Each such message will
feature an 'X-Fetchmail-Warning' header which is generated because
fetchmail cannot find a valid local name in the recipient addresses.
Such messages default (as was described above) to being sent to the
local user running fetchmail, but the program has no way to know that
this is actually the right thing.
Bad Ways To Abuse Multidrop Mailboxes
Multidrop mailboxes and fetchmail serving multiple users in daemon
mode do not mix. The problem, again, is mail from mailing lists,
which typically does not have an individual recipient address on it.
Unless fetchmail can deduce an envelope address, such mail will only
go to the account running fetchmail (probably root). Also, blind-
copied users are very likely never to see their mail at all.
If you are tempted to use fetchmail to retrieve mail for multiple
users from a single mail drop via POP or IMAP, think again (and reread
the section on header and envelope addresses above). It would be
smarter to just let the mail sit in the mail server's queue and use
fetchmail's ETRN or ODMR modes to trigger SMTP sends periodically (of
course, this means you have to poll more frequently than the mail
server's expiry period). If you cannot arrange this, try setting up a
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UUCP feed.
If you absolutely must use multidrop for this purpose, make sure your
mail server writes an envelope-address header that fetchmail can see.
Otherwise you will lose mail and it will come back to haunt you.
Speeding Up Multidrop Checking
Normally, when multiple users are declared fetchmail extracts
recipient addresses as described above and checks each host part with
DNS to see if it is an alias of the mail server. If so, the name
mappings described in the "to ... here" declaration are done and the
mail locally delivered.
This is a convenient but also slow method. To speed it up, pre-
declare mail server aliases with 'aka'; these are checked before DNS
lookups are done. If you are certain your aka list contains all DNS
aliases of the mail server (and all MX names pointing at it - note
this may change in a future version) you can declare 'no dns' to
suppress DNS lookups entirely and only match against the aka list.
Duplicate suppression on multidrop
If fetchmail's duplicate suppression code does not kick in for your
multidrop mail account, other options is using sieve, or for instance
Courier's maildrop package (and in particular, its reformail program
with the -D option) as the delivery agent (either from fetchmail, or
from your local mail server that fetchmail injects into).
SOCKS
Support for socks4/5 is a compile time configuration option. Once
compiled in, fetchmail will always use the socks libraries and
configuration on your system, there are no run-time switches in
fetchmail - but you can still configure SOCKS: you can specify which
SOCKS configuration file is used in the SOCKS_CONF environment
variable.
For instance, if you wanted to bypass the SOCKS proxy altogether and
have fetchmail connect directly, you could just pass
SOCKS_CONF=/dev/null in the environment, for example (add your usual
command line options - if any - to the end of this line):
env SOCKS_CONF=/dev/null fetchmail
EXIT CODES
To facilitate the use of fetchmail in shell scripts, an exit status
code is returned to give an indication of what occurred during a given
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connection.
The exit codes returned by fetchmail are as follows:
0 One or more messages were successfully retrieved (or, if the -c
option was selected, were found waiting but not retrieved).
1 There was no mail awaiting retrieval. (There may have been old
mail still on the server but not selected for retrieval.) If you
do not want "no mail" to be an error condition (for instance, for
cron jobs), use a POSIX-compliant shell and add
|| [ $? -eq 1 ]
to the end of the fetchmail command line, note that this leaves 0
untouched, maps 1 to 0, and maps all other codes to 1. See also
item #C8 in the FAQ.
2 An error was encountered when attempting to open a socket to
retrieve mail. If you do not know what a socket is, do not worry
about it -- just treat this as an 'unrecoverable error'. This
error can also be because a protocol fetchmail wants to use is
not listed in /etc/services.
3 The user authentication step failed. This usually means that a
bad user-id, password, or APOP id was specified. Or it may mean
that you tried to run fetchmail under circumstances where it did
not have standard input attached to a terminal and could not
prompt for a missing password.
4 Some sort of fatal protocol error was detected.
5 There was a syntax error in the arguments to fetchmail, or a pre-
or post-connect command failed.
6 The run control file had bad permissions.
7 There was an error condition reported by the server. Can also
fire if fetchmail timed out while waiting for the server.
8 Client-side exclusion error. This means fetchmail either found
another copy of itself already running, or failed in such a way
that it is not sure whether another copy is running.
9 The user authentication step failed because the server responded
"lock busy". Try again after a brief pause! This error is not
implemented for all protocols, nor for all servers. If not
implemented for your server, "3" will be returned instead, see
above. May be returned when talking to qpopper or other servers
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that can respond with "lock busy" or some similar text containing
the word "lock".
10 The fetchmail run failed while trying to do an SMTP port open or
transaction.
11 Fatal DNS error. Fetchmail encountered an error while performing
a DNS lookup at startup and could not proceed.
12 BSMTP batch file could not be opened.
13 Poll terminated by a fetch limit (see the --fetchlimit option).
14 Server busy indication.
23 Internal error. You should see a message on standard error with
details.
24 - 26, 28, 29
These are internal codes and should not appear externally.
When fetchmail queries more than one host, return status is 0 if any
query successfully retrieved mail. Otherwise the returned error status
is that of the last host queried.
FILES
$FETCHMAILHOME/fetchmailrc
~/.fetchmailrc, $HOME/.fetchmailrc, $HOME_ETC/.fetchmailrc,
default run control file (location can be overridden with
environment variables)
~/.fetchids, $HOME/.fetchids, $HOME_ETC/.fetchids, $FETCHMAILHOME/.fetchids
default location of file recording last message UIDs seen per
host. (location can be overridden with environment variables)
$FETCHMAILHOME/fetchmail.pid
~/.fetchmail.pid, $HOME/.fetchmail.pid, $HOME_ETC/.fetchmail.pid,
default location of lock file (sometimes called pidfile or PID
file, see option pidfile) to help prevent concurrent runs (non-
root mode). (location can be overridden with environment
variables)
~/.netrc, $HOME/.netrc, $HOME_ETC/.netrc
your FTP run control file, which (if present) will be searched
for passwords as a last resort before prompting for one
interactively. (location can be overridden with environment
variables)
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/var/run/fetchmail.pid
lock file (pidfile) to help prevent concurrent runs (root mode,
Linux systems).
/etc/fetchmail.pid
lock file (pidfile) to help prevent concurrent runs (root mode,
systems without /var/run).
ENVIRONMENT
Fetchmail's behavior can be altered by providing it with environment
variables. Some may alter the operation of libraries that fetchmail
links against, for instance, OpenSSL. Note that in daemon mode, you
will need to quit the background daemon process and start a new
fetchmail daemon for environment changes to take effect.
FETCHMAILHOME
If this environment variable is set to a valid and existing
directory name, fetchmail will read $FETCHMAILHOME/fetchmailrc
(the dot is missing in this case), $FETCHMAILHOME/.fetchids
(keeping its dot) and $FETCHMAILHOME/fetchmail.pid (without dot)
rather than from the user's home directory. The .netrc file is
always looked for in the invoking user's home directory (or
$HOME_ETC) regardless of FETCHMAILHOME's setting.
FETCHMAILUSER
If this environment variable is set, it is used as the name of
the calling user (default local name) for purposes such as
mailing error notifications. Otherwise, if either the LOGNAME or
USER variable is correctly set (e.g., the corresponding UID
matches the session user ID) then that name is used as the
default local name. Otherwise getpwuid(3) must be able to
retrieve a password entry for the session ID (this elaborate
logic is designed to handle the case of multiple names per user
ID gracefully).
FETCHMAIL_DISABLE_CBC_IV_COUNTERMEASURE
(since v6.3.22): If this environment variable is set and not
empty, fetchmail will disable a countermeasure against an SSL CBC
IV attack (by setting SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS). This
is a security risk, but may be necessary for connecting to
certain non-standards-conforming servers. See fetchmail's NEWS
file and fetchmail-SA-2012-01.txt for details. Earlier fetchmail
versions (v6.3.21 and older) used to disable this countermeasure,
but v6.3.22 no longer does that as a safety precaution.
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FETCHMAIL_POP3_FORCE_RETR
(since v6.3.9): If this environment variable is defined at all
(even if empty), fetchmail will forgo the POP3 TOP command and
always use RETR. This can be used as a workaround when TOP does
not work properly.
FETCHMAIL_INCLUDE_DEFAULT_X509_CA_CERTS
(since v6.3.17): If this environment variable is set and not
empty, fetchmail will always load the default X.509 trusted
certificate locations for SSL/TLS CA certificates, even if
--sslcertfile and --sslcertpath are given. The latter locations
take precedence over the system default locations. This is
useful in case there are broken certificates in the system
directories and the user has no administrator privileges to
remedy the problem.
FETCHMAIL_WOLFSSL_DEBUG
(since v6.4.25): If fetchmail is compiled and linked with
wolfSSL, if wolfSSL was built with --enable-debug, and if this
environment variable is set and not empty, then enable wolfSSL's
debug mode. This will emit huge amounts of debug output to
stderr.
HOME (documented since 6.4.1): This variable is normally set to the
user's home directory. If it is set to a different directory than
what is in the password database, HOME takes precedence.
HOME_ETC
(documentation corrected to match behaviour of code since 6.4.1):
If the HOME_ETC variable is set, it will override fetchmail's
idea of $HOME, i. e. fetchmail will read .fetchmailrc, .fetchids,
.fetchmail.pid and .netrc from $HOME_ETC instead of $HOME (or if
HOME is also unset, from the passwd file's home directory
location).
If HOME_ETC and FETCHMAILHOME are both set, FETCHMAILHOME takes
precedence and HOME_ETC will be ignored.
SOCKS_CONF
(only if SOCKS support is compiled in) this variable is used by
the socks library to find out which configuration file it should
read. Set this to /dev/null to bypass the SOCKS proxy.
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SSL_CERT_DIR
(with truly OpenSSL 3.0 compatible library): overrides OpenSSL's
idea of the default trust directory or path (which contains
individual certificate files and hashed symlinks), see the
SSL_CTX_set_default_verify_paths(3) manual page for details, it
may be in the openssl development package. If using another
library's OpenSSL compatibility interface, this may not work.
Since this variable only specifies a default value, the option
--sslcertpath takes precedence if given.
SSL_CERT_FILE
(with truly OpenSSL 3.0 compatible library): overrides OpenSSL's
idea of the default trust certificate bundle file (which contains
a concatenation of base64-encoded certificates in PEM format),
see the SSL_CTX_set_default_verify_paths(3) manual page for
details, it may be in the openssl development package. If using
another library's OpenSSL compatibility interface, this may not
work. Since this variable only specifies a default value, the
option --sslcertfile takes precedence if given.
other system default variables
such as TZ or the locale LC_XXX variables, will also influence
program behaviour.
SIGNALS
If a fetchmail daemon is running as root, SIGUSR1 wakes it up from its
sleep phase and forces a poll of all non-skipped servers. For
compatibility reasons, SIGHUP can also be used in 6.3.X but may not be
available in future fetchmail versions.
If fetchmail is running in daemon mode as non-root, use SIGUSR1 to
wake it (this is so SIGHUP due to logout can retain the default action
of killing it).
Running fetchmail in foreground while a background fetchmail is
running will do whichever of these is appropriate to wake it up.
BUGS, LIMITATIONS, AND KNOWN PROBLEMS
Please check the NEWS file that shipped with fetchmail for more known
bugs than those listed here.
Fetchmail cannot handle user names that contain blanks after a "@"
character, for instance "demonstr@ti on". These are rather uncommon
and only hurt when using UID-based --keep setups, so the 6.X.Y
versions of fetchmail will not be fixed.
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Fetchmail cannot handle configurations where you have multiple
accounts that use the same server name and the same login. Any
user@server combination must be unique.
The assumptions that the DNS and in particular the checkalias options
make are not often sustainable. For instance, it has become uncommon
for an MX server to be a POP3 or IMAP server at the same time.
Therefore the MX lookups may go away in a future release.
The mda and plugin options interact badly. In order to collect error
status from the MDA, fetchmail has to change its normal signal
handling so that dead plugin processes do not get reaped until the end
of the poll cycle. This can cause resource starvation if too many
zombies accumulate. So either do not deliver to a MDA using plugins
or risk being overrun by an army of undead.
The --interface option does not support IPv6 and it is doubtful if it
ever will, since there is no portable way to query interface IPv6
addresses.
The RFC822 address parser used in multidrop mode chokes on some @-
addresses that are technically legal but bizarre. Strange uses of
quoting and embedded comments are likely to confuse it.
In a message with multiple envelope headers, only the last one
processed will be visible to fetchmail.
Use of some of these protocols requires that the program send
unencrypted passwords over the TCP/IP connection to the mail server.
This creates a risk that name/password pairs might be snaffled with a
packet sniffer or more sophisticated monitoring software. Under Linux
and FreeBSD, the --interface option can be used to restrict polling to
availability of a specific interface device with a specific local or
remote IP address, but snooping is still possible if (a) either host
has a network device that can be opened in promiscuous mode, or (b)
the intervening network link can be tapped. We recommend the use of
ssh(1) tunnelling to not only shroud your passwords but encrypt the
entire conversation.
Use of the %F or %T escapes in an mda option could open a security
hole, because they pass text manipulable by an attacker to a shell
command. Potential shell characters are replaced by '_' before
execution. The hole is further reduced by the fact that fetchmail
temporarily discards any set-uid privileges it may have while running
the MDA. For maximum safety, however, do not use an mda command
containing %F or %T when fetchmail is run from the root account
itself.
Fetchmail's method of sending bounces due to errors or spam-blocking
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and spam bounces requires that port 25 of localhost be available for
sending mail via SMTP.
If you modify ~/.fetchmailrc while a background instance is running
and break the syntax, the background instance will die silently.
Unfortunately, it cannot die noisily because we do not yet know
whether syslog should be enabled. On some systems, fetchmail dies
quietly even if there is no syntax error; this seems to have something
to do with buggy terminal ioctl code in the kernel.
The -f~- option (reading a configuration from stdin) is incompatible
with the plugin option.
The 'principal' option only handles Kerberos IV, not V.
Interactively entered passwords are truncated after 63 characters. If
you really need to use a longer password, you will have to use a
configuration file.
A backslash as the last character of a configuration file will be
flagged as a syntax error rather than ignored.
The BSMTP error handling is virtually nonexistent and may leave broken
messages behind.
Send comments, bug reports, gripes, and the like to the fetchmail-
devel list
An fetchmail FAQ (in HTML form) is available at the fetchmail home
page, it should also accompany your installation.
AUTHOR
Fetchmail is currently maintained by Matthias Andree and Rob Funk with
major assistance from Sunil Shetye (for code) and Rob MacGregor (for
the mailing lists).
Most of the code is from Eric S. Raymond Too many other people to name
here have contributed code and patches.
This program is descended from and replaces popclient, by Carl Harris
the internals have become quite different, but some of its interface
design is directly traceable to that ancestral program.
This manual page has been improved by Matthias Andree, R. Hannes
Beinert, and H['e]ctor Garc['i]a.
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SEE ALSO
README, README.SSL, README.SSL-SERVER, The Fetchmail FAQ mutt(1),
elm(1), mail(1), sendmail(8), popd(8), imapd(8), netrc(5), the
fetchmail home page (alternative URI) the maildrop home page.
APPLICABLE STANDARDS
Note that this list is just a collection of references and not a
statement as to the actual protocol conformance or requirements in
fetchmail.
SMTP/ESMTP:
RFC 821, RFC 2821, RFC 1869, RFC 1652, RFC 1870, RFC 1983, RFC
1985, RFC 2554.
mail:
RFC 822, RFC 2822, RFC 1123, RFC 1892, RFC 1894.
POP2:
RFC 937
POP3:
RFC 1081, RFC 1225, RFC 1460, RFC 1725, RFC 1734, RFC 1939, RFC
1957, RFC 2195, RFC 2449.
APOP:
RFC 1939.
RPOP:
RFC 1081, RFC 1225.
IMAP2/IMAP2BIS:
RFC 1176, RFC 1732.
IMAP4/IMAP4rev1:
RFC 1730, RFC 1731, RFC 1732, RFC 2060, RFC 2061, RFC 2195, RFC
2177, RFC 2683.
ETRN:
RFC 1985.
ODMR/ATRN:
RFC 2645.
OTP: RFC 1938.
LMTP:
RFC 2033.
GSSAPI:
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RFC 1508, RFC 1734, Generic Security Service Application Program
Interface (GSSAPI)/Kerberos/Simple Authentication and Security
Layer (SASL) Service Names
TLS: RFC 2595.
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