formail - Unix, Linux Command
formail - mail (re)formatter
formail [+skip] [-total] [-bczfrktedqBY] [-p prefix]
[-D maxlen idcache]
[-x headerfield] [-X headerfield]
[-a headerfield] [-A headerfield]
[-i headerfield] [-I headerfield]
[-u headerfield] [-U headerfield]
[-R oldfield newfield]
[-n [maxprocs ]]
[-m minfields] [-s [command [arg ...]]]
formail is a filter that can be used to force mail into mailbox format, perform
From escaping, generate auto-replying headers, do simple
header munging/extracting or split up a
mailbox/digest/articles file. The mail/mailbox/article contents will be
expected on stdin.
If formail is supposed to determine the sender of the mail, but is unable
to find any, it will substitute foo@bar.
If formail is started without any command line options, it will force any
mail coming from stdin into mailbox format and will escape
all bogus From lines with a >.
Formail will print its version number and exit.
Dont escape any bogus mailbox headers (i.e., lines starting with From ).
-p prefix |
Define a different quotation prefix. If unspecified it defaults to >.
Assume traditional Berkeley mailbox format, ignoring any
Concatenate continued fields in the header. Might be convenient when
postprocessing mail with standard (line oriented) text utilities.
Ensure a whitespace exists between field name and content.
Zap fields which contain only a single whitespace character.
Zap leading and trailing whitespace on fields extracted with
Force formail to simply pass along any non-mailbox format (i.e., dont
generate a From line as the first line).
Generate an auto-reply header. This will normally throw away all the existing
fields (except X-Loop:) in the original message, fields you wish to preserve
need to be named using the
-i option. If you use this option in conjunction with
-k, you can prevent the body from being escaped by also specifying
When generating the auto-reply header or when extracting fields, keep
the body as well.
Trust the sender to have used a valid return address in his header. This
causes formail to select the
header sender instead of the
envelope sender for the reply. This option should be used when generating auto-reply
headers from news articles or when the sender of the message is
expecting a reply.
The input will be split up into separate mail messages, and piped into
a program one by one (a new program is started for every part).
-s has to be the last option specified, the first argument following it is
expected to be the name of a program, any other arguments will be
passed along to it. If you omit the program, then formail will simply
concatenate the split mails on stdout again. See
-n [maxprocs] |
Tell formail not to wait for every program to finish before starting
the next (causes splits to be processed in parallel).
Maxprocs optionally specifies an upper limit on the number of concurrently
Do not require empty lines to be preceding the header of a new message
(i.e., the messages could start on every line).
Tell formail that the messages it is supposed to split need not be in
strict mailbox format (i.e., allows you to split digests/articles or
non-standard mailbox formats). This disables recognition of the
-l folder |
Generate a log summary in the same style as procmail. This includes
the entire "From " line, the Subject: header field, the folder, and
the size of the message in bytes. The mailstat command can be used
to summarize logs in this format.
Makes formail assume that it is splitting up a BABYL rmail file.
-m minfields |
Allows you to specify the number of consecutive headerfields formail
needs to find before it decides it found the start of a new message, it
defaults to 2.
Tells formail to (still detect but) be quiet about write errors,
duplicate messages and mismatched
Content-Length: fields. This option is on by default, to make it display the messages
-D maxlen idcache |
Formail will detect if the Message-ID of the current message has
already been seen using an
idcache file of approximately
maxlen size. If not splitting, it will return success if a duplicate has been
found. If splitting, it will not output duplicate messages. If used
in conjunction with
-r, formail will look at the
mail address of the envelope sender
instead at the Message-ID.
-x headerfield |
Extract the contents of this
headerfield from the header. Line continuations will be left intact; if you
want the value on a single line then youll also need the
-X headerfield |
-x, but also preserves/includes the field name.
-a headerfield |
Append a custom
headerfield onto the header; but only if a similar field does not exist yet. If
you specify either one of the field names
Resent-Message-ID: with no field contents, then formail will generate a unique message-ID
-A headerfield |
Append a custom
headerfield onto the header in any case.
-i headerfield |
-A, except that any existing similar fields are renamed by prepending an
Old- prefix. If
headerfield consists only of a field-name, it will not be appended.
-I headerfield |
-i, except that any existing similar fields are simply removed. If
headerfield consists only of a field-name, it effectively deletes the field.
-u headerfield |
Make the first occurrence of this field unique, and thus delete all
subsequent occurrences of it.
-U headerfield |
Make the last occurrence of this field unique, and thus delete all
preceding occurrences of it.
-R oldfield newfield |
Renames all occurrences of the fieldname
Skip the first
skip messages while splitting.
Output at most
total messages while splitting.
When renaming, removing, or extracting fields, partial fieldnames may
be used to specify all fields that start with the specified value.
By default, when generating an auto-reply header procmail selects the
envelope sender from the input message. This is correct for vacation
messages and other automatic replies regarding the routing or delivery
of the original message. If the sender is expecting a reply or the
reply is being generated in response to the contents of the original
message then the -t option should be used.
RFC822, the original standard governing the format of Internet mail
messages, did not specify whether Resent header fields (those that
begin with Resent-, such as Resent-From:) should be considered
when generating a reply. Since then, the recommended usage of the
Resent headers has evolved to consider them as purely informational and
not for use when generating a reply. This has been codified in
RFC2822, the new Internet Message Format standard, which states in part:
While formail now
ignores Resent headers when generating header replies, versions of
formail prior to 3.14 gave such headers a high precedence. If the old
behavior is needed for established applications it can be specified by
calling formail with the option -a Resent- in addition
to the -r and -t options. This usage is deprecated
and should not be used in new applications.
Resent fields are used to identify a message as having been
reintroduced into the transport system by a user. The purpose of
using resent fields is to have the message appear to the final
recipient as if it were sent directly by the original sender, with
all of the original fields remaining the same....They
MUST NOT be used in the normal processing of replies or other such
automatic actions on messages.
While splitting, formail assigns the message number currently being output to
this variable. By presetting FILENO, you can change the initial message
number being used and the width of the zero-padded output. If FILENO is
unset it will default to 000. If FILENO is non-empty and
does not contain a number, FILENO generation is disabled.
To split up a digest one usually uses:
formail +1 -ds >>the_mailbox_of_your_choice
To remove all Received: fields from the header:
To remove all fields except From: and Subject: from the header:
formail -k -X From: -X Subject:
To supersede the Reply-To: field in a header you could use:
formail -i "Reply-To: foo@bar"
To convert a non-standard mailbox file into a standard mailbox file you can
formail -ds <old_mailbox >>new_mailbox
Or, if you have a very tolerant mailer:
formail -a Date: -ds <old_mailbox >>new_mailbox
To extract the header from a message:
To extract the body from a message:
RFC822, RFC2822, RFC1123
Too many processes on this machine.
Content-Length: field exceeds actual length by nnn bytes
The Content-Length: field in the header specified a length that was longer
than the actual body. This causes this message to absorb a number of
subsequent messages following it in the same mailbox.
Couldnt write to stdout
The program that formail was trying to pipe into didnt accept all the data
formail sent to it; this diagnostic can be suppressed by the
Duplicate key found: x
The Message-ID or sender x in this message was found in the idcache; this
diagnostic can be suppressed by the
Failed to execute "x"
Program not in path, or not executable.
File table full
Too many open files on this machine.
Invalid field-name: "x"
The specified field-name "x" contains control characters, or cannot be a
partial field-name for this option.
You can save yourself and others a lot of grief if you try to avoid using
this autoreply feature on mails coming through mailinglists. Depending
on the format of the incoming mail (which in turn depends on both the
original senders mail agent and the mailinglist setup) formail could
decide to generate an autoreply header that replies to the list.
In the tradition of UN*X utilities, formail will do exactly what
you ask it to, even if it results in a
non-RFC822 compliant message. In particular, formail will let you generate
header fields whose name ends in a space instead of a colon. While
this is correct for the leading From line, that line is not a
header field so much as the message separator for the mbox mailbox
format. Multiple occurrences of such a line or any other colonless
header field will be considered by many mail programs, including
formail itself, as the beginning of a new message. Others will
consider the message to be corrupt. Because of this, you should
not use the
-i option with the From line as the resulting renamed line,
Old-From , will probably not do what you want it to. If
you want to save the original From line, rename it with the
-R option to a legal header field such as X-From_:.
When formail has to generate a leading From line it normally will contain
the current date. If formail is given the option -a Date:,
it will use the date from the Date: field in the header (if present).
However, since formail copies it verbatim, the format will differ from that
expected by most mail readers.
If formail is instructed to delete or rename the leading From line, it
will not automatically regenerate it as usual. To force formail to regenerate
it in this case, include -a From .
If formail is not called as the first program in a pipe and it is told to
split up the input in several messages, then formail will not terminate until
the program it receives the input from closes its output or terminates itself.
If formail is instructed to generate an autoreply mail, it will
never put more than one address in the To: field.
Formail is eight-bit clean.
When formail has to determine the senders address, every
mail address is allowed. Formail will always strip down the address to
its minimal form (deleting excessive comments and whitespace).
The regular expression that is used to find real postmarks is:
"\n\nFrom [\t ]*[^\t\n ]+[\t ]+[^\n\t ]"
Content-Length: field is found in a header, formail will copy the number of specified bytes in
the body verbatim before resuming the regular scanning for message boundaries
(except when splitting digests or Berkeley mailbox format is assumed).
Any header lines immediately following the leading From line
that start with >From are considered to be a continuation
of the From line. If instructed to rename the From line,
formail will change each leading > into a space, thereby
transforming those lines into normal
Calling up formail with the -h or -? options will cause
it to display a command-line help page.
This program is part of the
procmail mail-processing-package (v3.22) available at http://www.procmail.org/ or
There exists a mailinglist for questions relating to any program in the
for subscription requests.
If you would like to stay informed about new versions and official patches send
a subscription request to
(this is a readonly list).
Stephen R. van den Berg
Philip A. Guenther