Cannot send mail between GroupWise and Exchange with Microsoft Small Business Server 2003

Cannot Send mail between Microsoft and Exchange
Mail from GroupWise to Exchange is seen Crossing the gateway and noted in Gateway logs.
Mail from GroupWise to Exchange is stuck in Exchange server MTS-IN Queue
Mail from Exchange is not seen in Queues or in logs
Microsoft Exchange MTA service is running and appears fine but is actually not functioning
Directory Sync for users in each system works correctly

Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall your operating system. Novell cannot guarantee that these problems can be solved.

Modify the registry at your own risk.

To resolve this problem, you must modify the registry to enable the MTA functionality. Before you start these steps, make sure that you have a good working system state backup. To resolve this problem, follow these steps:

1. Click Start, click Run, type regedit, and then click OK.
2. Locate the following registry sub key:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\name of your Exchange server computer\Private-guid_of_private_mdb
3. Delete the following two registry values:
   • Gateway In Threads
   • Gateway Out Threads
4. Locate the following registry sub key:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\name of your Exchange server computer\Public-guid_of_public_mdb
5. Delete the following two registry values:
   • Gateway In Threads
   • Gateway Out Threads
6. Quit Registry Editor.
7. Click Start, point to Administrative Tools, and then click Services.
8. Right-click Microsoft Exchange MTA Stacks, and then click Properties.
9. On the General tab, change the startup type to automatic, click Apply, and then click OK.
10. Right-click Microsoft Exchange MTA Stacks, and then click Start.
11. Right-click Microsoft Exchange System Attendant, and then click Restart. This procedure also restarts all dependant services.
12. Restart GroupWise Gateway for Microsoft Exchange.
13. Close the Services snap-in.

This problem occurs because the Microsoft Exchange MTA Stacks service and functionality is turned off. By default,  SBS 2003 disables the MTA Stacks service and functionality. Some third-party programs including the GroupWise Gateway for Microsoft Exchange install an Exchange connector that requires the MTA Stacks service to work correctly. Manually starting the MTA Stacks service may not resolve the problem.