I'm currentlxy working on installing Zimbra Opensource Editon on an ubuntu server. The domain for Zimbra should be mail.domain.tld.

My questionis the following:

Does the MX of domain.tld have to point to the Zimbra Server on installation? The MX record of domain.tld currently points somewhere else and should stay there at the moment. But I'd like to add mail accounts for several other domains. Is this possible?
What do I need to consider at installation?