[Mimedefang] Greylisting post-data (was Re: [PATCH] filter_data implementation)

David F. Skoll dfs at roaringpenguin.com
Wed May 27 21:17:31 EDT 2009

- wrote:

>> 1) To make greylisting work with marginal SMTP servers that don't handle
>> 4xx responses to RCPT properly.

> I can accept that - although I've never knowingly observed it.

Old versions of Novell Groupwise failed to handle this properly (though
it has been fixed for a long time.)  I believe the same applies to old
versions of Lotus Notes.

> However, if subject were not part of your mix, then greylisting
> (with a "421" as that's really the only temp-error code that should
> occur in response to DATA) would work.

421 responses to DATA probably cause seldom-tested code to
execute. :-) Many SMTP implementations don't handle edge cases in the
SMTP state machine very well.



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