Hi Stefan

> So the reject generates bounces at our spamfilters. Howto handle this?

Yes, I do know this issue, as we offer a similar service.

And I must admit, I have no real solution if you use some out of the
stock MTA like postfix or sendmail which work on store and forward
basis.

I also considered hacking together a small 'relay' MTA which would
receive the email but not reply OK to the final DATA command (RFC
states you can take up to 60 seconds to reply to the DATA command)

The relay MTA would perform virus / spamfiltering and then forward the
email to the destination MX.

When the Destination MX replies with OK to the DATA phase, and only
then, it would reply back, possibly forwarding the same OK messages it
received from upstream, to the sending side.

Pitfalls:

* 60 second according RFC, not every MSA respects this. Our Spamfilter
  sometimes takes a couple of seconds to scan the content after DATA. If
  it's too long, some MTA start re-sending the email multiple times.

* You have to possibly hold many connections open.

Mit freundlichen Grüssen

-Benoît Panizzon-
-- 
I m p r o W a r e   A G    -    Leiter Commerce Kunden
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