[Mimedefang] all_spam_to abuse

David F. Skoll dfs at roaringpenguin.com
Tue Feb 21 16:51:42 EST 2012

On Tue, 21 Feb 2012 13:38:04 -0800 (PST)
Chris Flav <chris.flav at yahoo.ca> wrote:

> Indeed the point of using MIMEdefang is the possibility to reject a
> email during the SMTP transaction, instead of accepting the email to
> only silently delete it later.

If different recipients have different policies, it's extremely difficult
to do that.  The SMTP protocol simply doesn't lend itself to that.

The only way to (1) apply different policies to different recipients,
(2) reject during the SMTP session and (3) not generate backscatter is
to group your recipients into policy-classes.  You need to accept RCPT To:
commands for the first recipient and all recipients in the same policy
class and tempfail all other RCPT To: commands.  Then you process the

In theory, the sender keeps trying the tempfailed recipients until all
policy classes have been processed.

In practice, this makes senders angry and introduces a lot of delays.
We've agonized over this with our commercial products and have decided
that sometimes silently discarding a message is the only viable option.



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