MX (CNAME) & forwarding

[Mathias Körber]

| > Setting up the same accounts with individual
| > forwarding on both sites would sure be messy.
| > Can this be solved domain-wise by MX entries?
| 
| Yes. An MX record essentially says "Mail to X should be 
| delivered to the following malserver(s)"
| 
| X    IN   MX    10   mailserver-1
| X    IN   MX    50   mailserver-used-as-backup
| 
| 
| Now one could have MX records in both x.com and x.net 
| pointing to the same mailserver(s) ( identical MX records ) 
| 
| One have to configure the mailserver to recognize itself as
| both x.com and x.net , this may be done
| with the 'Cw' macro ( or Fw entry ) in sendmail.cf

Let me add a bit: 

If this is all that is set up in sendmail, then both domains would
implicitly have the same users (i.e. user1 at x.com is the same as
user2 at x.net), as the server would simply treat the mail as for
user 'user1'.
Using sendmail's 'virtusertable' feature, one can however have
those accounts treated differently. For more details you'd have
to check the sendmail documentation and/or ask in a sendmail group.
That is, if you are using sendmail at all. Should you be using a different
MTA (e.g. postfix or qmail), ask in the respective forums for those
tools.

regards