We rebooted our Exchange server (Exchange 2003 SP2) after installing MS security updates. When the server came back up there were over 50 email messages in SMTP queue. Each had varying dates, and some dated back to the last time the server was rebooted (almost 2 months ago). All of the message recipients I looked at in the SMTP queues were from other domains (yahoo, gmail, etc.)
The Exchange server uses an SMTP connector, which happens to be our Barracuda anti-spam appliance. I have been administering the Exchange server for several months and haven't seen any messages lingering in the queues for more than 20 minutes, nor have I ever rebooted the server and then had mail flow, especially from two months ago.
I also have checked the Badmail folder and the Exchange Anti-Virus quarantine, I didn't see any of the messages that got sent out after the reboot.
There must be a folder I'm missing on the Exchange server that held these messages. When the Exchange server was rebooted on Friday, a brick level backup was running. I thought that perhaps the back up job being cut off like that may have explained why the messages suddenly appeared and went out. However, a user reported today that a message they sent last month arrived to it's intended recpipients last Friday night.