I have an old Exchange 5.5 server humming along fine. However I've noticed a few users' mailboxes are enormous. One user has over 12000 files in her mail box and i can see no obvious reason why ...

Exchange 2010 environments (2 separate ones.) I have a few customers with very large mailboxes (20+gb for all of them, some in the 40gb and 50gb ranges.) It runs great for the most part ...