I have recently deployed an Exchange 2010 SP1 server running on Server 2008 R2 SP1. Server 2008 is currently running on VMWare ESXi 4.1 along with 2 other 2008 instances (both running minimal services). My Exchange server has 8GB of the 24GB available memory allocated with the other servers only having 4GB allocated each, so there is plenty of spare memory. The physical server has 2 x E5620s (so a total of 8 CPUs). The hard drives are 6Gbs Near Line SAS drives.
Based on the Exchange hardware requirements, this setup should be able to host 6 mail boxes with out any issues. This server is running the following roles: Hub Transport, Client Access, and Mailbox.
The problem is, every other day or so, users will suddenly receive several emails that had been sent earlier. So for a 2 hour time span, our server will stop delivering messages, then it will suddenly deliver them all at once. E-Mails just prior to or after that time span, seem to deliver immediately, like they are supposed to.
I've been monitoring the CPU and Memory usage through out the day, and even when the issue is going on, and the CPU usage (with 4 allocated CPUs) is between 0% - 5%. So as far as I can tell it's not a CPU issue.
I have the default logging currently enabled and i do not see any strange logs in the event viewer.
Any help would be greatly appropriated.