We have aprox. 70 users at this point but had it running with aprox. 100 users for a while. We have Exchange 2000 sp1 running on it and nothing else. We have a Dell Poweredge 4400. Dual 866Mhz/256k PIII Xeon's 1 GB SDRAM With a total of 8 disks: 9 GB Raid 1 for the OS (2 hd) 9 GB Raid 1 for the Transaction Logs (2 hd) 18 GB Raid 5 for the Exchange Databases (3 hd) 18 GB Global Hotspare drive (1 hd) all this times two, we have a hotspare server with exactly the same config. sitting right next to it waiting to kick in (configuring this one is a whole separate story, too long to even mention it) We thought it was overkill at first but here we are more than a year and a half later and now I would've like to have gotten bigger disk capacity for our databases from the get go. No performance issues otherwise, other than some bouncing messages (NDR's) that caused virtual memory to be eaten up once, but that was a bug that was fixed calling Microsoft and applying one of those well hidden hotfixes (got reimbursed for the call though) As someone else said, it is better to overkill than to have to change your hardware a year from now. Remember it's an email server you are talking about, as trivial as it sounds it may be one of the most important servers in your company (at least in the eyes of your users and managerial staff).