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Re: EXITCODES, bounce, might be off topic

2002-04-19 15:30:29
Rui Pires asked,

| What is the exact path the bounce follows? Does it look to the
| Return-Path: field (often inexistent or as much crap as the From:)? Does
| it try to follow the path it took to reach my server, contacting the
| same servers for mail transfer?...

It goes to the envelope sender address as provided to the MTA in the MAIL
FROM: line of the SMTP dialogue.  That address might be in Return-Path:; it
might be nowhere in the visible headers at all.  Procmail generally does not
know it.

Bouncing spam from the LDA after the SMTP dialogue is over is a bad idea, and
you should remove those recipes.  The envelope sender address on a piece of
spam falls into one of three categories:

1. It's a nonexistent, perhaps syntactically invalid, address.  Your bounce
will go nowhere and your system's attempt to consult a nameserver and
transmit the bounce notice somewhere will just be a waste of cycles and
bandwidth.

2. It's the real address of someone other than the spammer, someone whom the
spammer is trying to harass by having the bounces go to that person for all
the copies of the spam sent to invalid addresses.  By sending yet another
bounce notice to the victim, you're making it worse on an innocent person who
is already suffering more than you from that piece of spam.

3. It's an address that goes back to the spammer -- but chances are 98% or
greater that the spammer couldn't care less and absolutely will not remove
your address from future mailings.  Chances are 100% that whoever sold your
address to the spammer is not going to remove it.

Rejecting spam during the SMTP dialogue is a different matter: that kind of
bounce will go to the system that initiated the connection [greatly reducing
the likelihoods of #1 and #2 above], it will keep the item out of your
mailbox, and it will save the trouble of running the LDA on that piece.  But
once the message gets into procmail's hands, that opportunity has passed,
even more so because the Return-Path: header might be forged and you'll have
even less chance of sending it to the party that deserves it.  Bouncing spam
from procmail can be pointless or mean, but it can never help.  Don't do it.





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