An A record is an MX record and is a missing MX....

Fri Apr 4 02:13:51 UTC 2003

At 03:58 PM 4/3/2003 -0600, Gerardo Gregory wrote:
>Since then I have learned that some MTA's will look for an A record if it 
>cannot find an MX record and use the A record instead.

This is always the case. MX records are only required if you want to have 
more than one mail exchange servers to serve your domain, e.g. if you want 
to have a secondary mail server as a relay if the primary server goes down.

If you only have one mail exchange server to serve your domain, you don't 
need MX records. An A record pointing to your mail server is sufficient.

-ip-