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

- kd6lvw at yahoo.com
Wed May 27 22:01:01 EDT 2009


--- On Wed, 5/27/09, David F. Skoll <dfs at roaringpenguin.com> wrote:
> Date: Wednesday, May 27, 2009, 6:17 PM - wrote:
> ...
> > 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.

Perhaps so, but in RFC 5321 (and predecessors, 2821 and 821), the ONLY tempfail code valid at that point is 421, so if these programs didn't plan for it, they failed to follow the historical design for an SMTP client, and are thus completely broken.

As spamware is also broken, perhaps we should assume that such a client is hostile?



More information about the MIMEDefang mailing list