finding trails in outlook

We recently had to let someone go from our company. We disabled the login account for NT but left the e-mail account intact so it could be accessed by a different account. We now suspect somone snooped around in the mailbox using the that account and sent files to the deleted folder.
How can I check when the messages were received and what account opened them and when the were deleted?
we are using Outlook 97 exchange 5.5 on NT 4.0 and IIS.

Thanks