Re: Anti-MailBomb

> How can I set up procmail to route my email to /dev/null if my mailbox
> gets more than a certain number of messages in it?
Wellll, as someone else already pointed out this is dangerous, but, I
also believe in free choice.  So, here goes.

Assuming that you meant your _system_ mailbox, here's how you can do
what you ask:

    # Set MAX_MAIL to the maximum number of messages
    MAX_COUNT=1000

    # Count how many messages in ORGMAIL.  This egrep fast, but possibly
    # inaccurate; it can be fooled by having "From " at the start of
    # lines in mail bodies.  It just means it might count a few extra.

    # BTW, the "test" is done to ensure that the maildrop really exists,
    # otherwise, the grep or formail split will wait on STDIN.
    :0
    * ? test -f $ORGMAIL
    { COUNT=`egrep -c '^From ' $ORGMAIL` }
    :0E
    { COUNT=0 }

    # If accuracy is important, uncomment this recipe, and comment the
    # one above.

    # The slow way, but, the "procmail" way :^)
    #:0
    #* ? test -f $ORGMAIL
    #{ XLIST=`formail -e -s echo -n x < $ORGMAIL`
    #  :0
    #  * XLIST ?? 1^1 x
    #  { COUNT = $= }
    #}
    #:0E
    #{ COUNT=0 }

    # Here's where the drop may occur
    :0
    * ? test $COUNT -gt $MAX_COUNT
    /dev/null

Let's suppose that you would rather have a limit on the maximum size of
the mail, and drop that way.

    MAX_SIZE=5000000            # 5 MBs maximum

    :0
    * ? test -f $ORGMAIL
    { SIZE=`wc -c <$ORGMAIL` }  # get size of system mailbox
    :0E
    { SIZE=0 }

    NEW_SIZE=`wc -c`            # get incoming mail size

    TOTAL_SIZE=`expr $NEW_SIZE + $SIZE`

    # If the total size exceeds the maximu, drop the mail
    :0
    * ? test $TOTAL_SIZE -gt $MAX_SIZE
    /dev/null

Now, dropping the mail isn't very nice to your correspondents.  You
should give them a choice of possibly sending it at a later time.  So,
bounce it back with a little message...

    # ... same preparation as above
    # Check on the total size
    :0
    * ? test $TOTAL_SIZE -gt $MAX_SIZE
    {
        LOCKFILE=bounced.lock           # protect the bounced.mail file
        JUNK=`rm -f bounced.mail`       # don't use old mail
        :0c
        bounced.mail                    # save a copy

        # Generate a reply header
        :0 fh
        | formail -rt   -I"From:  $LOGNAME's Mail-Daemon <$LOGNAME>" \
                        -I"Subject: Mail not delivered" \
                        -I"X-Loop: $LOGNAME" \
                        -I"Precedence: junk" \

        # Generate a reply body
        :0 fb
        | echo "Sorry, but your recent mail to $LOGNAME(_at_)$HOST (below)" ; \
          echo "could not be delivered for some reason." ; \
          echo "Your original message follows." ; \
          echo "-----------------------------------------------------" ; \
          cat bounced.mail

        LOCKFILE                        # ok to trash the stored mail

        # Deliver the composed bounce message
        :0
        ! -oi -t
    }

Hope this gives you a better understanding of procmail's versatility.

___________________________________________________________
Alan Stebbens       <stebbens(_at_)sgi(_dot_)com>       (415) 933-6437
Silicon Interactive Group,   Silicon Graphics, Inc.   (SGI)
M/S:9L991, 2011 N. Shoreline Blvd., Mountain View, CA 94043