Badmail   records   double-bounces:   messages   whose  recipient  was
nonexistent   or   otherwise   undeliverable,  AND  whose  sender  was
nonexistent or otherwise undeliverable. Since a bounce message was not
successfully accepted for delivery, the message content is archived.

So  you are greatly underestimating the problem if based solely on the
#  of  messages in Badmail. Backscatter consists of both _successfully
transmitted_  bounces  from  your  server in response to incoming spam
(bounces  successfully accepted for users whose address was spoofed to
send  spam),  and  _attempted_  bounces  that  were  not  accepted for
whatever   reason  (when  the  sender  address+domain  was  completely
randomized  and  nonexistent, when the domain existed but not the full
address,  or  when  the  sender  address was legit but the sender's MX
heuristically  detected  that your bounce was backscatter and rejected
it  at  the  envelope).  The  latter  case will end up in Badmail. The
former will not, by definition.

I  think  you're confusing two different sides of the battle. Incoming
bounces don't result in additional bounces generated by your server.

Spammers may use your domain as the sender, which results in you being
the _victim_ of backscatter.

Or  spammers  may use another domain as the sender and send to unknown
users  at  your  domain;  if you accept these messages and bounce them
afterward  (instead  of  rejecting them at the envelope), then you are
the  _creator_  of  backscatter  --  the victim being the impersonated
sender domain.

This sentence really doesn't add up. If you "don't use it for outgoing
mail at all", then who are the "recipients" who "reject it anyway"?

I agree that you are not relaying. But plenty of damage can be wreaked
without relaying.

--Sandy

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Sanford Whiteman, Chief Technologist
Broadleaf Systems, a division of
Cypress Integrated Systems, Inc.
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