Reverse lookup mx records and cnames

[schnitzelmeister at gmail.com]

Hello.
I'm not sure what to do.

I have lots of servers which have a record such as
 mail.customerdomain IN A 10.1.1.1
The MX record for each domain is something like
 customerdomain IN MX mail.customerdomain

This works fine, but you can get a listing of all customers by doing a
reverse lookup on 10.1.1.1, which is our mail server. This isn't good.

I've thought of two ways to fix this:
 1. Use a CNAME for the MX record to point to our mail server.
   This isn't allowed or recommended.
 2. Hack the reverse zone to only return our mail server name.
   This is a hack.

Can anyone offer me any advice?