We had an interesting problem with our Exchange environment that has left a mystery behind.
A couple days ago, we had a catastrophic failure that took both of our mailbox and transport servers offline for approximately 1 hour. After we got the servers back online, we had reports of email not making it to recipients, both internal and external. We looked everywhere for a problem, but we couldn't find any definite source, so we restarted the Exchange services on both servers. This fixed the mail flow problems, but now we cannot find any trace of the emails sent during this problem period.
Any ideas what would have happened, why emails were not left in users' outboxes, and why anything that didn't get delivered didn't throw an NDA at least? The emails DO appear in the users' sent items folder, just no record of them after that.