Possible Causes: Exchange Server 2003 has a feature that permits Exchange
2003 to operate without the Message Transfer Agent (MTA). If a message was
sent incorrectly by using the MTA route, this delivery status notification
is returned to the sender.
Note Although Exchange 2003 can operate without the MTA, Microsoft does not
recommend or support this configuration.
To turn on this feature and to prevent the messages from queuing to the MTA,
follow these steps:1. Disable the MTA service.
2. Set the DWORD value to 0 in the following registry subkeys for every
information store database and public folder store:
Name>\<PrivMDB_GUID>\Gateway In Threads
Name>\<PrivMDB_GUID>\Gateway Out Threads
When you do this, you are making store resources that are associated with
MTA delivery available.
3. Restart the information store.
Troubleshooting: Check your routing topology. Use the WinRoute tool to make
sure that the routes are correctly replicated between servers and routing
Not sure if the above is the problem, but worth checking into.