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[AMaViS-user] Avoiding multiple scan Kiss Gabor (Bitman) Thu Jun 03 14:00:58 2010

I have a spam filter host (actually it is a cluster but this does not matter)
that serves 2-3 MTAs simultaneously.
One of them is a list server the other is my smart host as well
as MX.
Now if I send a message to a mailing list. The following happens:

1. My desktop machine passes the mail to the smarthost.
2. The smarthost gives it to spamfilter.
3. The checked mail goes to list server.
4. The list server passes it to spamfilter. (i.e. the same as scanned
   it a seconds ago.
5. One of outgoing mails goes back to my MX (that is identical to my smart
6. MX asks spamfilter to scan the mail third time.
7. Mail arrives to my desktop host.

What can I do if I don't want to waste CPU cycles.
Is there any way to put a (cryptographically signed) certificate
into the header at the first scan like this "Already checked" ?
This mark could be recognized in all the following rounds so
amavisd could pass the message without further checks.

A simple "Received: by ..." header is not enough because it can be
forged easily by impostors.


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