[Mimedefang] Spam with more than one recipient - reject or not?

Steffen Kaiser skmimedefang at smail.inf.fh-bonn-rhein-sieg.de
Wed Sep 7 02:13:10 EDT 2005

On Tue, 6 Sep 2005, Wesley Peters wrote:

> On Wed, 2005-08-17 at 07:54 -0400, David F. Skoll wrote:
>> Michal Jankowski wrote:
>>> I have received a suggestion to stream by recipient.
>>> But that's a big no-no. Once you do that, you have effectively
>>> accepted the smtp transaction. So you cannot 'bounce' and the only way
>>> to notify sender is by mail, which should be avoided at all cost.
>> Well, in that case, you just discard instead of bounce.
>> Can you suggest a viable alternative?  (Other than re-writing SMTP, of course.)
> Tempfail all the recipients who use different rules than the first?

That's falls into the field of "re-writing SMTP"; because the recipients 
are sent amd acknowledged (or rejected)  _before_ the contents comes in, 
you can't tempfail individual recipients based on the contents.

Also, another idea:

+ tempfail the message awhole, &
+ when the mail transfer is attempted again, you know the old score and 
tempfail the recipients, who does not like the mail.

Well, won't work as well, because when the recipients are sent, you only 
know the connecting host, the HELO string and the envelope sender. Not 
enough information to reliably identify a message.
Some (mostly larger hosters) have mail clusters, where, possibly, a 
message is retried from another host, which should use another HELO string 
as well.

So one can only act on the tuple (sender, recipient), and, you can't even 
rely on that the order of the recipients keeps the same on retry.
-> Well, this is much like conditional greylisting, where you hope that 
the attempt for re-transfer is a good sign for non-SPAM.


Steffen Kaiser

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