Software

The EDB limit used to be hard coded at 16GB in Exchange 2000, and the default is 18GB in Exchange 2003. Since I forget which Exchange Service Pack, MS allowed this limit to be modified to up to 75GB with a registry edit. Yours evidently has been increased from the default of 18GB to 68GB, and remember, 75GB is the max, period.

If you're flirting with this limit, I would suggest,
a) deploying another exchange server,
b) creating another Storage Group or groups and migrating some user mailboxes to the new group(s), or
c) beating the users into submission and doing a defrag (eseutil /d priv1.edb) on the mailbox store.

http://technet.microsoft.com/en-us/library/aa998066.aspx

http://support.microsoft.com/kb/830408

Please post back if you have any more problems or questions.