fetchmail - Unix, Linux Command

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.


If
fetchmail is used with a POP or an IMAP server, 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 are intended for a single
recipient.  An individual mail message will not be inspected for recipient
information, rather, the identity of the recipient will either default to
the local user currently executing fetchmail,
or else will need to be explicitly specified in the configuration file.
Singledrop-mode is used when the fetchmailrc configuration contains at
most a single local user specification for a given server account.


With multidrop-mode,
fetchmail is not able to assume that there is only a single recipient, but rather
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 an MTA, however it is important to note that neither
the POP nor IMAP protocols were intended for use in this fashion, and
hence envelope information is often not directly available.  Instead,
fetchmail must resort to a process of informed guess-work in an attempt to
discover the true envelope recipient of a message, unless the ISP stores
the envelope information in some header (not all do).  Even if this
information is present in the headers, the process can
be error-prone and is dependent upon the specific mail server used
for mail retrieval.  Multidrop-mode is used when more than one local
user is specified for a particular server account in the configuration
file.  Note that the forgoing discussion of singledrop- and
multidrop-modes does not apply to the ESMTP ETRN or ODMR retrieval
methods, since they are based upon the SMTP protocol which
specifically provides the envelope recipient to fetchmail.


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 locally via your system’s MDA (Mail Delivery Agent, usually
sendmail(8) but your system may use a different one such
as smail, mmdf, exim, postfix, or qmail).  All the
delivery-control mechanisms (such as .forward files) normally
available through your system MDA and local delivery agents will
therefore work automatically.


If no port 25 listener is available, but your fetchmail configuration
was told about a reliable local MDA, it will use that MDA for local
delivery instead.


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 be present on your
system.  If you are 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 mailserver supports, and warn you of potential problems
with that server.




Each server name that you specify following the options on the
command line will be queried.  If you don’t specify any servers
on the command line, each ’poll’ entry in your
~/.fetchmailrc file will be queried.


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
in sections on AUTHENTICATION and DAEMON MODE which follow.


Note that fetchmail may still try to negotiate TLS even if this option
is not given. You can use the --sslproto option to defeat this
behavior or tell fetchmail to negotiate a particular SSL protocol.


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 /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).


NOTE: If you use client authentication, the user name is fetched from the
certificate’s CommonName and overrides the name set with --user.



        openssl x509 -in cert.pem -noout -md5 -fingerprint


For details, see
x509(1ssl).



        --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.


A word of warning: 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 though. Using
maildrop(1)
is usually much easier, and many users find the filter syntax used by
maildrop easier to understand.




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.



        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.


Note that this option may be removed from a future fetchmail version.


This option changes the header
fetchmail assumes will carry a copy of the mail’s envelope address.  Normally
this is ’X-Envelope-To’, but as this header is not standard, 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, and it should not be necessary
unless you have globally disabled Received parsing with ’no envelope’
in the .fetchmailrc file.


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.


’Delivered-To:’


message header.  Whenever qmail delivers a message to a local mailbox
it puts the username and hostname 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.




If the mailserver 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:


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 mailserver 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.  See the
ftp(1)
man page for details of the syntax of the
~/.netrc file.  To show a practical example, a .netrc might look like
this:

machine hermes.example.org
login joe
password topsecret


This feature may allow you to avoid duplicating password
information in more than one file.


On mailservers 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 don’t know
the correct user-id and password for your mailbox account.


Early versions of POP3 (RFC1081, RFC1225) supported a crude form of
independent authentication using the
rhosts file on the mailserver 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.


fetchmail will always use the RETR command if "fetchall" is set.
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.


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 mailserver 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 mailserver.


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 V, so you’re 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 ’ssh’ 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
authentication instead of sending over the password en clair if it
detects "@compuserve.com" in the hostname.


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 en clair) 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.


You can access SSL encrypted services by specifying the --ssl option.
You can also do this using the "ssl" user option in the .fetchmailrc
file. With SSL encryption enabled, queries are initiated over a connection
after negotiating an SSL session, and the connection fails if SSL cannot
be negotiated.  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. The --sslproto option can be used to select the SSL
protocols (default: v2 or v3).  The --sslcertck command line or
sslcertck run control file option should be used to force strict
certificate checking - see below.


If SSL is not configured, fetchmail will usually opportunistically try to use
TLS. TLS can be enforced by using --sslproto "TLS1". TLS
connections use the same port as the unencrypted version of the
protocol and negotiate TLS via special parameter. The --sslcertck
command line or sslcertck run control file option should be used to
force strict certificate checking - see below.


--sslcheck 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. Use of the sslcertck or --sslcertck
option is advised.


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 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 doesn’t help against an
active attacker. It’s 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,
http://monkey.org/~dugsong/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.


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.




Example: simply invoking


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,
fetchmail sets up a per-user lockfile 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 aren’t polling the same server with two processes at the
same time.)


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

authentication or multiple timeouts.


The option
--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.


The
-L <filename> or
--logfile <filename> option (keyword: set logfile) is only effective when fetchmail is
detached. 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 aren’t 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).


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’s turned on in the
~/.fetchmailrc file, or that the
-L or
--logfile <file> option was used.


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. Note that this also causes the logfile option to be
ignored (though perhaps it shouldn’t).


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 mailserver) but not delivered
locally due to some transient error, it will be re-fetched during the
next poll cycle.  (The IMAP logic doesn’t delete messages until
they’re 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 also that if you break the
~/.fetchmailrc file’s syntax, the new instance will softly and silently vanish away
on startup.




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.  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
mailserver host.


The
--showdots option (keyword: set showdots) forces fetchmail to show progress dots
even if the current tty is not stdout (for example logfiles).
Fetchmail shows the dots by default when run in nodetach mode or when
daemon mode is not enabled.


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’.




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’ve already read on the
server are being fetched (and deleted) even when you don’t specify
--all.  There are several reasons this can happen.


One could be that you’re using POP2.  The POP2 protocol includes no
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 can’t make tempfiles 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 isn’t the right thing
to do, fetchmail should check the UIDVALIDITY and use UID, but it
doesn’t 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’s not specified by the IMAP RFCs.  If you ever trip over
a server that doesn’t, 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.




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".


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
multidropped 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 won’t 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.






To protect the security of your passwords,
your ~/.fetchmailrc may not normally have more than 0600 (u=rw,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.


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 descriptions.  Note: the most common cause of syntax
errors is mixing up user and server options.


For backward compatibility, the word ’server’ is a synonym for ’poll’.


You can use the noise keywords ’and’, ’with’,
’has’, ’wants’, and ’options’ anywhere in an entry to make
it resemble English.  They’re ignored, but but can make entries much
easier to read at a glance.  The punctuation characters ’:’, ’;’ and
’,’ are also ignored.






Here are the legal global options:




Here are the legal server options:




Here are the legal user options:




Remember that all user options must follow all server 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 sometime useful
for ignoring bogus envelope headers created by an ISP’s local delivery
agent or internal forwards (through mail inspection systems, for
instance).


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
mailserver 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 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.


The ’is’ or ’to’ keywords associate the following local (client)
name(s) (or server-name to client-name mappings separated by =) with
the mailserver 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
mailserver.  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 hostname parts
that match your poll name or your ’via’, ’aka’ or ’localdomains’
options, and usually also for hostname parts which DNS tells it are
aliases of the mailserver.  See the discussion of ’dns’, ’checkalias’,
’localdomains’, and ’aka’ for details on how matching addresses are
handled.


If fetchmail cannot match any mailserver 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 mailserver username is recognized
attached to a matching hostname part, its local mapping is added to
the list of local recipients.


The ’checkalias’ option (normally off) extends the lookups performed
by the ’dns’ keyword in multidrop mode, providing a way to cope with
remote MTAs that identify themselves using their canonical name, while
they’re 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 vs. 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 mailserver, 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 hostname
netaxs.com, but any hostname 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 mailserver 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 mailserver
will be aborted.


Similarly, the ’postconnect’ keyword similarly allows you to specify a
shell command to be executed just after each time a mailserver
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 it 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 mailservers in order to avoid mail loops but
may get in your way if you try to "mirror" a mailserver 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
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 doesn’t 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.




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’, ’ssh’, ’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 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.  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).




For solving hardware-induced segfaults, find the faulty component and repair or
replace it. <http://www.bitwizard.nl/sig11/> may help you with details.


For solving software-induced segfaults, the developers may need a "stack
backtrace".




1. To get useful backtraces, fetchmail needs to be installed without
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.





        Return-Path:
        Resent-Sender: (ignored if it doesn’t contain an @ or !)
        Sender: (ignored if it doesn’t contain an @ or !)
        Resent-From:
        From:
        Reply-To:
        Apparently-From:


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 doesn’t exist, the bounce message
won’t 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 Received: header (or whichever one is
specified by the ’envelope’ option) to determine the local
recipient address. If the mail is addressed to more than one recipient,
the Received line won’t 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 don’t 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.)




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"


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’s a version of those two 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;


This version is much easier to read and doesn’t cost significantly
more (parsing is done only once, at startup time).




If you need to include whitespace in a parameter string, enclose the
string in double quotes.  Thus:



  poll mail.provider.net with proto pop3:
        user "jsmith" there has password "u can’t 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’s possible to specify more than one user per server (this is only
likely to be useful when running fetchmail in daemon mode as root).
The ’user’ keyword leads off a user description, and every user specification
in a multi-user entry must include it.  Here’s an example:



  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’s 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’s an example of another kind of multidrop connection:



  poll pop.provider.net localdomains loonytoons.org toons.org:
        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!


Here’s 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 ssh;
        user esr is esr here




Also, note that in multidrop mode duplicate mails are suppressed.  A
piece of mail is considered duplicate if it has the same message-ID 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.




Sometimes
fetchmail can deduce the envelope address.  If the mailserver 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 doesn’t work reliably for other MTAs, nor if there is
more than one recipient.  By default, 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’s 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 the
mailserver 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’re fetching from (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).




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’ll 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
isn’t removed from alias expansions in messages you send.


This trick is not without its problems, however.  You’ll 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 that’s actually the right thing.




If you’re 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
mailserver’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 mailserver’s expiry period).  If you can’t arrange
this, try setting up a UUCP feed.


If you absolutely must use multidrop for this purpose, make sure
your mailserver writes an envelope-address header that fetchmail can
see.  Otherwise you will lose mail and it will come back
to haunt you.




This is a convenient but also slow method.  To speed
it up, pre-declare mailserver aliases with ’aka’; these are checked
before DNS lookups are done.  If you’re certain your aka list contains
all DNS aliases of the mailserver (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.




The exit codes returned by
fetchmail are as follows:






If the environment variable FETCHMAILHOME is set to a valid and
existing directory name, fetchmail will read $FETCHMAILHOME/fetchmailrc
(the dot is missing in this case), $FETCHMAILHOME/.fetchids and
$FETCHMAILHOME/.fetchmail.pid rather than from the user’s home
directory.  The .netrc file is always looked for in the the invoking
user’s home directory regardless of FETCHMAILHOME’s setting.


If the HOME_ETC variable is set, fetchmail will read
$HOME_ETC/.fetchmailrc instead of ~/.fetchmailrc.


If HOME_ETC and FETCHMAILHOME are set, HOME_ETC will be ignored.




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.




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 6.3.X versions of
fetchmail won’t be fixed.


Please check the NEWS file that shipped with fetchmail for more
known bugs than those listed here.


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 don’t get reaped until the end
of the poll cycle.  This can cause resource starvation if too many
zombies accumulate.  So either don’t 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 mailserver.
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 suid privileges it may have while running the
MDA.  For maximum safety, however, don’t 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 and
spam bounces requires that port 25 of localhost be available for sending
mail via SMTP.


If you modify a
~/.fetchmailrc while a background instance is running and break the syntax, the
background instance will die silently.  Unfortunately, it can’t
die noisily because we don’t 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.


Send comments, bug reports, gripes, and the like to the
fetchmail-devel list <fetchmail-devel@lists.berlios.de>.  An HTML FAQ is
available at the fetchmail home page; surf to
http://fetchmail.berlios.de/ or do a WWW search for pages with
’fetchmail’ in their titles.




Most of the code is from Eric S. Raymond <esr@snark.thyrsus.com>.  Too
many other people to name here have contributed code and patches.


This program is descended from and replaces
popclient, by Carl Harris <ceharris@mal.com>; 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 R. Hannes Beinert and H[’e]ctor
Garc[’i]a.




The fetchmail home page: <http://fetchmail.berlios.de/>


The maildrop home page: <http://www.courier-mta.org/maildrop/>


Note that this list is just a collection of references and not a
statement as to the actual protocol conformance or requirements in