The MTA handles message transfer between domains.
The message flow diagrams in GroupWise 2012 Troubleshooting 3: Message Flow and Directory Structure focus on TCP/IP links because they are the most common and convenient (unless you have two domains on the same server). For diagrams that include mapped/UNC links, see GroupWise 6.5 Troubleshooting 3: Message Flow and Directory Structure on the GroupWise 6.5 Documentation Web site. For an explanation of link types and link protocols, see
Understanding Link Configuration in
Domains in the GroupWise 2012 Administration Guide.