When installing a signed encryption certificate last night I made a typographical error that caused outbound mail to get stuck in queue and not send.
I discovered that someone was wrong this morning when a customer sent me e-mail around 8am, (incoming and local to local was good).
It took me four hours to find it but it has been corrected, all mail in queue is sent, and mail is processing normally.
I will be taking this system down about five minutes after midnight Saturday morning June 8th (just after midnight tonight) to image the machine now that I have it in a working configuration.