formail - mail (re)formatter
formail [+skip] [-total] [-vbczfrktedqBY] [-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 `>'.
-v Formail will print its version number and exit.
-b Don't escape any bogus mailbox headers (i.e. lines starting with `From
Define a different quotation prefix. If unspecified it defaults to
-Y Assume traditional Berkeley mailbox format, ignoring any Content-
-c Concatenate continued fields in the header. Might be convenient when
postprocessing mail with standard (line oriented) text utilities.
-z 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.
-f Force formail to simply pass along any non-mailbox format (i.e. don't
generate a `From ' line as the first line).
-r 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.
-k When generating the auto-reply header or when extracting fields, keep
the body as well.
-t 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 gen-
erating auto-reply headers from news articles or when the sender of
the message is expecting a reply.
-s 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 splitted mails on stdout again. See FILENO.
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 run-
-e Do not require empty lines to be preceding the header of a new message
(i.e. the messages could start on every line).
-d 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
-B Makes formail assume that it is splitting up a BABYL rmail file.
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.
-q 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 -q-.
-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.
Extract the contents of this headerfield from the header, display it
as a single line.
Same as -x, but also preserves the field name.
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.
Append a custom headerfield onto the header in any case.
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.
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.
Make the first occurrence of this field unique, and thus delete all
subsequent occurrences of it.
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 into newfield.
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 mes-
sages 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 mes-
sages, 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 changed
to consider them as purely informational and not for use when normally gen-
erating a reply. 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 dis-
To split up a digest one usually uses:
formail +1 -ds >>the_mailbox_of_your_choice
formail +1 -ds procmail
To remove all Received: fields from the header:
formail -I Received:
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:
formail -X ""
sed -e '/^$/ q'
To extract the body from a message:
formail -I ""
sed -e '1,/^$/ d'
mail(1), binmail(1), sendmail(8), procmail(1), sed(1), sh(1), RFC822,
Can't fork 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.
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 char-
acters, or cannot be a partial field-name for this
No-wait option ignored to prevent corrupt idcache
The -n and -D options cannot be safely used togeth-
er, so the former was ignored.
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 gen-
erate an autoreply header that replies to the list.
When formail has to generate a leading `From ' line it normally will con-
tain 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 regen-
erate 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 un-
til the program it receives the input from 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 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).
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 (v3.14) avail-
able at http://www.procmail.org/ or ftp.procmail.org in pub/procmail/.
There exists a mailinglist for questions relating to any program in the
for submitting questions/answers.
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