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]

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 `>'.

-b 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 `>'.

-Y Assume traditional Berkeley mailbox format, ignoring any Content-Length: fields.

-c Concatenate continued fields in the header. Might be convenient when postprocessing mail with standard (line oriented) text utilities.

-z Ensure a space exists between field name and content. Zap fields which contain only a space. 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 option will be most useful when generating auto-reply headers from news articles. If this option is not turned on, formail tends to favour machine-generated addresses in the header.

-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.

-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.

-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 Content-Length: field.

-B 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.

-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 sender instead at the Message-ID.

-x headerfield
Extract the contents of this headerfield from the header, display it as a single line.

-X headerfield
Same as -x, but also preserves 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 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 case.

-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 into newfield.

+skip Skip the first skip messages while splitting.

-total Output at most total messages while splitting.


To split up a digest one usually uses: or

To remove all Received: fields from the header:

To remove all fields except From: and Subject: from the header:

To supersede the Reply-To: field in a header you could use:

To convert a non-standard mailbox file into a standard mailbox file you can use:

Or, if you have a very tolerant mailer:

To extract the header from a message:


To extract the body from a message:


mail(1), binmail(1), sendmail(8), procmail(1), sed(1), sh(1), RFC822, RFC1123

Can't fork

Content-Length: field exceeds actual length by nnn bytes

Couldn't write to stdout

Duplicate key found: x

Failed to execute "x"

File table full

Invalid field-name: "x"

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.

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 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 (delet- ing excessive comments and whitespace).

The regular expression that is used to find `real' post- marks is:

If a Content-Length: field is found in a header, formail will copy the number of specified bytes in the body verba- tim 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-pack- age (v3.11pre7 1997/04/28) available at your nearest USENET comp.sources.misc archive, or at ftp.infor- as pub/packages/procmail/procmail.tar.gz.

There exists a mailinglist for questions relating to any program in the procmail package:
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Stephen R. van den Berg