Mailserver requirements

Mon Apr 5 21:21:21 UTC 2004

On Mon, 05 Apr 2004 23:03:05 +0200, Arnold Nipper <arnold at 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....
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