We're running Exchange 2003 Enterprise and our store has grownfrom 16GB 2 years ago to 90GB currently across 135 mailboxes. Yes, yes, I know ... we need quotas in place. Several of our users have mailboxes in the 4GB range. Are there any recommendations/best practiceson per user mailbox size limits? Are there performance hits when mailboxes get to_GB in size? (we have cached mode enabled for everyone) Backup/restore problems aside, I'd like to be able to point to some reference info before setting quotas in place. If there's no real performance/health reasons why a mailbox shouldn't be 4GB then it's harder to justify setting a quota below that. Right now I'm just guessing that a 4GB mailbox isn't a great idea, but no one is complaining that email is slow. Secondly, what about a 90GB store? Good/Bad/indifferent? I see that Exchange2007 recommends only 100GB...doh! Both our frontend and backend exchange servers are virtual (VMware Server). They live on different host servers but both have dual xeon 3GHz procs with 4GB ram (I believe the backend VM has 3GB ram and the frontend gets 1GB). Simultaneous users hitting exchange is at most 50. Thanks, Jason

Hi Jason, Here is a link that you may find interesting: http://msexchangeteam.com/archive/2006/07/06/428213.aspx "Thinking about Mailbox and Message Size Limits" On another note. You may want to also read Microsoft's take on running Exch on vmware :) http://support.microsoft.com/?kbid=897615 "Support policy for Microsoft software running in non-Microsoft hardware virtualization software"