You must run an MTA for each domain. The MTA:
Routes messages between post offices in the local domain.
Routes messages between domains.
Routes messages to and from gateways installed in the local domain.
Routes messages between GroupWise systems across the Internet if appropriate DNS lookup capabilities have been set up.
Schedules routing of messages across expensive links.
Controls the size of messages that can pass across links.
Updates the domain database (wpdomain.db) whenever GroupWise users, resources, post offices, or other GroupWise objects are added, modified, or deleted.
Replicates updates to all domains and post offices throughout your GroupWise system. This keeps the Address Book up-to-date for all GroupWise users.
Synchronizes GroupWise user information with Novell eDirectory user information. This handles updates made in ConsoleOne without the GroupWise Administrator snap-in running.
Synchronizes GroupWise object information throughout your GroupWise system as needed.
Detects and repairs invalid information in the domain database (wpdomain.db).
Provides logging and statistics about GroupWise message flow.