formail - mail (re)formatter
] [-p prefix
] [-D maxlen
] [-l folder
] [-x headerfield
] [-a headerfield
] [-i headerfield
] [-u headerfield
] [-R oldfield newfield
]] [-m minfields
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.
- Don't 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
- 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 -x.
- Force formail to simply pass along any non-mailbox format
(i.e., don't 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 -b.
- 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 FILENO.
- -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 running processes.
- 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 Content-Length: field.
- -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
- -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 use
- -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
- -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 you'll also need the -c option.
- -X headerfield
- Same as -x, but also preserves/includes the field
- -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 Message-ID: or Resent-Message-ID: with no
field contents, then formail will generate a unique message-ID for you.
- -A headerfield
- Append a custom headerfield onto the header in any
- -i headerfield
- Same as -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
- Same as -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 oldfield
- 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.
, 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:
- 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 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.
- 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 use:
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:
- Can't fork
- Too many processes on this machine.
- Content-Length: field exceeds actual length by nnn
- 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.
- Couldn't write to stdout
- The program that formail was trying to pipe into didn't
accept all the data formail sent to it; this diagnostic can be suppressed
by the -q option.
- 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 -q option.
- 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
sender's 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
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
more than one address in the `To:' field.
Formail is eight-bit clean.
When formail has to determine the sender's address, every RFC822
conforming 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 ]"
If a 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 RFC822
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
available at http://www.procmail.org/ or ftp.procmail.org in
There exists a mailinglist for questions relating to any program in the procmail
for submitting questions/answers.
for subscription requests.
If you would like to stay informed about new versions and official patches send
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(this is a readonly list).
Stephen R. van den Berg
Philip A. Guenther