Greylisting...

[John Rudd]

Glenn Steen wrote:

> Just a small observation: I see that you (IMO rightly) reject the
> domain literal (MX IP address) too... This _technically_ breaks RFC
> compliance.

There was just a discussion about this over on the mimedefang mailing list.

What the RFC (2821?) prohibits is rejection based on the HELO/EHLO given 
hostname not resolving to the IP address of the submitter.

You can reject for other reasons.  Like they gave you your own domain 
name.  Or your own IP address.  That's rejecting for a different reason 
than "the IP address and Hostname don't match".  As long as the reason 
isn't literally "I looked up the name they gave me in the Helo, and it 
didn't resolve to the IP address I'm talking to".

Them giving you your own hostname, of course, is logically the same as 
them giving you a hostname that doesn't match their IP address, but your 
reason for rejecting it is "it's _MY_ hostname", so that doesn't violate 
the RFC prohibition.