Ok, so I've got an Exchange 5.5 server which is a DC & MX host.
It's DNS host name is "mail.mydomain.com", but it's computer name
name is "mailsvr.internet.local". This is the name that it uses
in the HELO command and there doesn't seem to be a way to change
this without changing the machine name - a total non-started for a DC!
(I didn't write AD or Exchange so don't blame me).
Actually, if your computer announces itself as "mailsvr.internet.local"
in HELO, then nothing is going to help you. Any HELO check would try
to get the SPF record for "mailsvr.internet.local" and promptly fail
since ".local" isn't a valid TLD.
- Mark