IMHO there are reasons for the EHLO or HELO to use the internal server
name, which may not be associated with a public IP Address, so expecting
the EHLO to match the PTR can and will get you into trouble.
It is more important to make sure that the domain in the PTR record, has
a URL associated..
There are those that try to make sure that forward/reverse match, but
they often do that wrong.. (eg only one forward needs to match the reverse).
Just always make sure that your EHLO is a FQDN, not just a hostname, and
for gods' sake not an IP literal, or 'localhost.localdomain' etc..
Public resources need to be transparent, HELO/EHLO is an identifier, and
often an internal identifier, rather than a public one. Make sense?
On 2023-10-27 06:19, Cyril - ImprovMX via mailop wrote:
Hi!
It's been quite common to refuse a server connecting that doesn't have a
proper PTR, but I was wondering if there was any recommendation (either
official via RFC or standard practice) about a server connecting with a
PTR that is different from the announced hostname at the HELO/EHLO command.
For instance, if my server has a PTR with mail1.example.com
<http://mail1.example.com>, and I connect by saying "HELO
send.example.com <http://send.example.com>". If the receiving server
loads all the IPs for "send.example.com <http://send.example.com>" but
doesn't find my server's IP, should it refuse the email or accept it ?
Thank you for your help here.
Best regards,
Cyril
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