I was talking to someone today and they said that real world experience says that you shouldn't have more than 250 users in an information store (Exchange 2003) for performance reasons. I have been under the assumption that the only real limits were purely based of the particular scenario (such as disaster recovery expectations, disk IO, number of items in mailboxes, etc). So, is there any validity to the statement, or is it more scenario based? What about with Exchange 2000?