We are currently in the process of migrating from sendmail to Zimbra. We have MX records setup for mail.domain.com and mail02.domain.com. The original server is mail.domain.com and mail02.domain.com is the zimbra server. We have about 75 users on the old sendmail server and 3 users on Zimbra. Our architecture is currently setup with all mail coming into mail.domain.com and then if its one of the 3 Zimbra users it forwards to the Zimbra server.

The problem is we setup zimbra to be @mail02.domain.com and the original is @domain.com. Whats the best way to migrate from @mail02.domain.com while still allowing mail to be received at both places depending on whether the user exists or not? Basically both servers (sendmail and Zimbra) need to accept @domain.com and have the mail go to the appropriate place.

Sendmail is running on Fedora Core 5 and Zimbra is running on RHEL4 for reference. Any help would be appreciated.