There is a great video from Dave's Garage about this: https://youtu.be/pBmuY6qFMPQ

I think the thing to take away from this is the poor state of management/maintenance tools that Exchange had. Thankfully over the years this has improved, but in those early years it was pretty bad.

I was using both Exchange and Lotus Notes/Domino in that period. If the same thing had happened in Notes, we'd just shut down the mail router task, open the mail.box database and remove the offending message. Easy. But that can only be done because Notes re-used its database system for everything, including the mail queue.

Exchange has a history of reinventing the wheel even within its own architecture. Let's just say I'mm very grateful that we're now on Microsoft 365 and these things are Microsoft's problem, not mine... 😉