How to configure email domains (The target principal name is incorrect)

Hi guys!

I need some help regarding configuration of mail domains.

I named my server as server1.mydomain.com and added several domains, eg domain1.com, domain2.com....
I created all needed DNS records, as well as mail.domain1.com, mail.domain2.com, ...

When in email client I use mail.domain1.com I get "The target principal name is incorrect" for certificate, because postfix and dovecot use certificate generated for server1.mydomain.com. If in email clients I put server1.mydomain.com for server address, everything is ok (which is expected).
I could live with using server1.mydomain.com at the moment, but if I expand cluster and move domains to other servers, you have to bother updating each client address eg from server1. to server2.

Anyway, I would like to use proper mail. address for each domain, and I can't make it work.

What are my options here?