I have been monitoring our Exchange Server for a couple of days and we are seeing CPU spikes and performance hits during the day. During this time we see a trying to connect to the exchange server pop-up on our desktops. We also are not seeing any connectivity issues with the network at this time. We run Exchange 2003 SP2. We have increased our mailbox store size over the 16 gig limit, but our actual size is 13 gigs for the private store and 3 for the public. We have 3.2 GHz Pentium 4 server grade machine with 2 gigs of ram and 15K SCSI Raid 5. Our transaction logs are always less than 100 and are never more than a day or so old. We do not use any retention policies, but we do set mailbox limits. We have about 70 users with about 25 having a 600 meg limit, the rest range from 300 megs to 100 megs. At times when moving large amounts of messages within a mailbox we can see the CPU performance stay at 100%. What really concerns me is when looking at the store is the amount of data in the mailboxes. More than half of the users with the 600 meg limit are almost at the limit and have item counts of 19,000 items, 13,000 items, 15,000 items, 8,000 items, etc. I thought that the item count should be kept down as well as this does more harm than actual size of the messages. Aside from upgrading the server CPU itself, does the item count seem to be the main culprit here? I know more ram could help, but would it seem to me the first step would be to clean out the mailboxes.