We've just completed a migration from Exchange Server 5.5 to Exchange Server 2003. For security reasons, we want to turn off all unnecessary services. Is the MTA Stacks service necessary?
Even if you aren't using Exchange 5.5 (and thus have no need for X.400 Message Transfer Agent-MTA-capability), the MTA Stacks service must remain enabled. If you disable the service, various features—most notably the ability to use Exchange System Manager (ESM) to move mailboxes between servers—will stop working.