We run E2k (enterprise edition) SP3 on W2k SP2. I never heard of absolute size limits for a mailbox itself, but when I tried to set the Storage Limits for one particularly large mailbox to 2.5 GB, I got the error: "The value for ... is not valid. Specify a value from 0 through 2097151". MS Technet does not have any reports on this (as far as I could find out).
Does this mean one cannot have a mailbox larger than 2 GB, or does it simply mean that you cannot set Storage limits beyond that point? This is rather urgent, since the mailbox belongs to a director and there might be some consequences to this story for us...