How to edit the DNS template?

Hello,

I am trying to figure out the correct syntax in order to change the default MX hostname to a custom one however I haven't succeeded so far. Can you please help?

It should work like this: If mail is enabled on the new virtual server, the MX record with priority 5 must be a specific hostname (i.e mail.mydomain.com) for ALL servers and NOT the default hostname which is the mail.$DOM

How can I do this?

${IF-MAIL} ...???? ${ENDIF-MAIL}

Any help is much appreciated N