Max Concurrent Inbound Connections

I have a branch office which runs 2 POA's and 2 MTA's. One of the PO's
has no users and is being decommisioned. The other PO has 8 users.

However, BOTH MTA's have started complaining that the Max Concurrent
Inbound Connections has been reach.

Initially it was 40 (the default). I then raised it to 80. Same result.
After about 1 - 2 hours this error occurs. Evenutally, the POA starts
to complain that the tranfter port is not available.

I have both MTA's on Verbose logging but that's not telling me anything.

How do I debug what's going on here ? (GW 8.01)

Steve