Over the last 4-5 days, I have been experiencing an issue with my Exchange 2003 server where Outlook 2007 clients will disconnect and receive an error message stating (paraphrase) "Outlook is retrieving data from the server" Also during this time, I have noticed that store.exe will grow rapidly up to over 1 GB of memory used.....although, I am not sure what a benchmark for it was before all of this began happening. I am working on an inter-forest migration and have been pretty frequent on the Migration forum while working on that. I have made a configuration that will forward all mail for unresolved recipients over to a Hub Transport server in the target forest running Exchange 2007. In addition, I have created an Accepted Domain on the target domain (2007 side) and have created an SMTP connector on the 2007 target side to route all of the messages from the 2007 (target) side out through the Exchange 2003 server to use it as a smart host. However, I don't think these configuration changes could have caused this issue since I don't have any "real" users (and only a couple of test mailboxes) over on the 2007 side. I am jsut preparing for the migration now. In addition to all of that, I ran with EXPBA and EXTRA tools today. The EXTRA tool stated that I had a Disk Bottleneck Issue on the drive that hosts my Private Store. This drive is also hosting Ninja Quarantine/Anti-Spam (Sunbelt) and BackupExec Remote Agent and I know that is not a best practice however it's been set up on the same drive like that for years. I am completely stumped as to what to do next. I have checked many of the performance recommendations and they're all there but I will be happy to check them again at your direction. I have updated NIC drivers and storage drivers today (firmware too) and have added Exclusions into my A/V scanner. I have also defragmented the Exchange database as well as the drive that the database is hosted on. Right now, store.exe is over 1 GB in memory use and growing. I am expecting that I will most likely see this drop-out again tomorrow and the only recourse I've found is to restart the server. Please help and thank you!

IF you disable the Ninja and AV, does the problem continue? Have you updated Exchange 2003 to the latest hotfixes as well?

I updated drivers for NIC and storage (firmware too) and did not see any issues today. Also, turned off CheckSum Offload on the NIC properties and added the MS recommended exclusions for AV. I'm not sure any of these was the magic fix as today (Friday) is a lower usage day for the mailserver. I have not run into any issues today though, so I will continue to monitor. Yes, Exchange is fully updated although I understand there's another patch coming out Tuesday (4/13/10). Thanks for the response and I will post back on Monday if I continue to see some interruption as it will be a higher utilization day.