foad

Section: (1)
Updated: 13 Jan 2001
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NAME

foad - f* off and die spam

SYNOPSIS

foad [-bhntv] [-c .foadrc]

DESCRIPTION

foad reads anchored case-insensitive extended regular expressions, which may be anchored, from $HOME/.foadrc representing/matching the users valid e-mail addresses and mailing lists and reads an e-mail message's headers from stdin via procmail(1), extracts the From:, To:, Cc:, Bcc: and their Resent-*: counter-parts. These headers are split and trimmed down to just the addresses. For example, "joe shmoe" <joe@foo.com> is reduced to joe@foo.com and mail lists such as 'mail-list-foo: ;' to mail-list-foo:. Then the regexes are applied to each of the addresses reduced from the headers until there is a match or there are no more comparisons to be made.

These functions could be done with procmail(1) with multiple recipes, but this method uses one recipes and is IMO easier to manage.

OPTIONS

-b: Also egrep Bcc: and Resent-Bcc: headers. These headers are only seen in mail originating on the delivery host and even then only with some MTAs.
-c .foadrc: Specify an alternate run-config file. The default is $HOME/.foadrc.
-f: Also egrep From: and Resent-From: headers.
-h: Print usage info and return exit code 1.
-n: Negate the exit code. This applies to all exit codes here, but with the stipulation that when parsing command-line arguments, foad may exit before the negate option is parsed and therefore the exit code would not be negated.
-t: Read $HOME/.foadrc and return exit code 1 (0, if negate option is supplied) on error. This tests reading the configuration file and compiling the regexes.
-v: Print version tag and exit.

SAMPLE RUN-CONFIG

$HOME/.foadrc may contain, one per-line, comments beginning with ^# and anchored or un-anchored case-insensitive extended regular expressions. See egrep(1) for specifics on extended regex formats, etc.

    # comment
    # match joe@domain.net or joe@something.domain.net
    joe@([^[:space:]]+.)?domain.net
    # match joe@domain.net, exactly
    ^joe@domain.net$
    # mail lists
    # match nanog@merit.edu or nanog-something@merit.edu
    nanog(-[^[:space:]]+)?@merit.edu
    # <EOF>

PROCMAIL RECIPES

foad is intended to be run via procmail(1). Below are two sample procmailrc(5) recipes. One of these should be added as the last recipe in your .procmailrc, or second to last if you have a default recipe.

    # this recipe will save headers of filtered messages
    # (when foad exits with exit code 0, aka. no matches)
    # to the file $MAILDIR/spam
    #
    :0 W h:
    * ? /usr/local/bin/foad
    $MAILDIR/spam

    # this recipe will save the entire filtered messages
    # (when foad exits with exit code 0, aka. no matches)
    # to the file $MAILDIR/spam
    #
    :0 W:
    * ? /usr/local/bin/foad
    $MAILDIR/spam

The destination for filtered mail ($MAILDIR/spam) could be /dev/null to dump the spam altogether. However, it is important to note that there is no way to (reliably) match valid email that was blind carbon copied (bcc) to the recipient, because the bcc: header will not be included at final delivery in most cases. Senders that send valid bcc'd email can either be matched in the recipients .procmailrc or add to the .foadrc and invoke foad with the -f option.

There is also an issue when senders use a MUA that hides recipient addresses behind a mail list tag such as 'mail-list-foo: ;'. The problem here is that the tag is free-form. So, while these are reduced as mentioned above, it can change at the whim of the user and there can be as many different tags as there are users. These could be matched with the regex ^[^ ]+:$, but this method is often used by spammers. Personally, i choose to match known tags, such as that for the IETF secretariat and filter the rest, which are usually garbage anyway.

EXIT STATUS

If a successful match is made, foad returns exit code 1, else 0.

The exit code will also be 1 if an invalid command line option is specified, an error occurs while reading the rc file ( .foadrc ), parsing the mail headers, or while compiling and or executing the regexes. This means that a run-time error will be treated like a match, from procmail's perspective, and filtering will not occur.

FILES

$HOME/.foadrc: Default run-config file.

This document was created by man2html, using the manual pages.
Time: 16:44:16 GMT, February 10, 2023