OT: SORBS a PITA on spam backscatter ...

[Garry Glendown]

Sorry, this is most likely somewhat off topic, but maybe I could get
some suggestions ...

One of our customers was hit by a presumably larger amount of spam
mails, addressed to mail addresses collected somehow, but with errors in
the addresses (first part of the mail address duplicated, like
"johnjohn at do.main" instead of "john at do.main"). They are operating a
multi-level mail service, with MS on our side, delivering to an SMTP
proxy, then over through a virus scanner, and finally to the actual mail
server (M$ Exchange). Mails are accepted, even by the Exchange server,
which in turn generates a non-delivery receipt for wrong addresses.

For outgoing mail, our central mail server is the smarthost. Which in
turn got listed on SORBS for delivering spam backscatter ... great. As
far as I see it, delivering the mails, which in themselves are generated
in compliance with RFCs, is fully legitimate.

What should we do? We get complaints due to the fact that certain mails
sent from other customers are being blocked on recipient mailservers due
to our server being SORBS-listed ...

I personally do not see any way of identifying whether such a receipt
(if I'm able to even decide that it is a non-delivery receipt) is for
legitimate mails that couldn't be delivered, or for spam.

Any suggestions?

tnx, -garry

-- 
Orwell war ein Optimist