Messages awaiting directory lookup - Email Queuing

Messages are queuing in the "Messages awaiting directory lookup" queue.


General Configuration information:


Exchange 2003 SP 1 Server A
Internet Mail Connector 1 configured as a Smart Host to DMZ Server A (IIS 6.0 SMTP Gateway) with a cost of (1)
(4) 2.0 GHz Procs - 4GB Memory - Tuned for Large Memory
GB Ethernet - second adapter disabled

Exchange 2003 SP1 Server B
Internet Mail Connector 2 configured as a Smart Host to DMZ Server B (IIS 6.0 SMTP Gateway) with a cost of (1)
(4) 2.0 GHz Procs - 4GB Memory - Tuned for Large Memory
GB Ethernet - second adapter disabled

Exchange 2003 SP1 Server C
Internet Mail Connector 1 configured as a Smart Host to DMZ Server A (IIS 6.0 SMTP Gateway) with a cost of (10) ** Server used for Application Server relay
(4) 2.0 GHz Procs - 4GB Memory - Tuned for Large Memory
GB Ethernet - second adapter disabled


8 Procs on the E2K3 SP1 MBX Cluster A / 4 Procs on the (2) E2K3 Public Folder Servers for a total of 28 E2K3 Processors.

We currently have 2 High-End GC's dedicated to Exchange 2003 - 8 Procs so we fall within the range of the 4:1 recommended ratio.

There are E5.5 boxes in the primary site but I have not added them to the equation as of yet.


Many of the settings are default with the exception of the relay settings which are restricted by subnet and the size restrictions which we use a standard of 5120kb.

The Issue -
During peak hours the awaiting directory lookup queues are starting to fill up. All perf counters return solid values, no event events are being generated that really point to a specific issue ... I've tried adding more GC's (2-3) and still had the same results.

I didn't have this issue until I upgraded to SP1 - I also rebuilt one of the IMS servers the same night. Now I'm having issues with all of the servers.

I apologize if this isn't enough info ... I'm more or less looking for potential issues I should look into, rather than a solution (unless you have one!) :)

Thanks,
Brian