On Mon, 05 Apr 2004 23:03:05 +0200, Arnold Nipper <arnold@nipper.de> said:
Today I run across a MTA which refused to accept mail because it could not detect an MX record for the reverse mapping of the IP address of the server which tried to deliver mail. Is this correct?
Depends on your definition of "correct". Checking that there's a PTR and A record that match has become common, although not strictly standard. Checking that said PTR points to a hostname that has an MX is certainly "way out there".
Or: if A is the IP Address of server trying to deliver mail, does mx(reverse(A)) have to exist?
There's no RFC requirement that an MX exist at all (only that you check for an MX before using the A record). The last 2 AOL boxes I got mail from were omr-m07.mx.aol.com and rly-ye05.mail.aol.com. I'm not seeing an MX for either of those. Draw your own conclusions as to whether a Randy Bush quote is needed....