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Re: How to prevent being a 'bouncer' of evil mail?

Yves Junqueira wrote:
> In one of my implementations, I have a gateway that filters messages,
> removing most spam and viruses, than redirect them to the appropriate
> servers. Thus, I do not have a record of user accounts for those
> domains. What usually happens is that I get messages for
> "xzx9z89z@mydomain.tld", from "someone@yahoo.com", and after the
> final server gets the message, it bounces to yahoo.
> I don't want to cause any trouble to other admins. I understand the
> way that smtp works, and that I must issue DSN's for undelivered
> messages. But is there any mixture of techniques to avoid bugging
> yahoo or other servers? Or have I missed the idea of DSN's?

Figure out how to get a list of valid final recipients to your gateway-
then that machine can reject recipients that doesn't exist.  Further
processing is up to the sending server- or, in the case of most spam and
viruses, the spamware or virus SMTP engine (which most likely will just
discard that recipient for that run).

The details of how to get such a list to into your gateway's SMTP
software depend on what your final delivery servers are running, and
what you're running on your gateway.

>From what you've described, you're stuck with one or more hideous SMTP
systems like Exchange that insists on accepting everything before
rejecting unknown users with a *new* message (rather than an SMTP
rejection code) as the final server.

"Sendmail administration is not black magic.  There are legitimate
technical reasons why it requires the sacrificing of a live chicken."
   - Unknown

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