Exchange 5.5 – SP3 MTA Queues

I am seeing repeating issues on our Clustered Exchange Bridgehead Sever, where the MTA Queues are getting backlogged as the day goes on.

If you look at the queues the majority of entries are Directory Service’s with some email’s.

There does not seem to be any real reason as to why this happeing. To resolve the issue we currently failover the cluster, i.e reboot one of the servers and the queues then clear very fast.

All Our other MSX Servs are running Service Pack 4 for Exchange.

Does anyone have any ideas on how to solve/fix this problem ?