Default Mail Server in 3.0

I have a question regarding mail server and IW 3.0

If I decided to run a dedicated mail server, I know I could manually redirect the MX record in the Zone to point all mail to this hypothetical dedicated mail server.

Is there a way to have IW automatically add the MX record for the dedicated mail server instead when a site is automatically created on the IW server?

Also what would be the best way to allow a dedicated mail server be the default mail server for all IW servers yet keep the functionality of creating mailboxes in SiteWorx?