My theory was, when they switched from LotusNotes to Outlook, they never ported over years of worth of experience encoded in user permissions. At least that fits well with the warning people always give about re-writing legacy software....
It's probably because he felt that he was in a position of expertise and authority that he tried to pre-empt the problem by telling everyone not to reply to the list. One last message to all, then the problem would be definitively solved, or so the logic would go.
I don’t quite why so few people break reply storms in this way. Bcc isn’t _that_ mysterious.
In a recent experience, I Replied to All (in BCC) to explain how BCC works and all the replies to my email stayed off the list.
https://www.theregister.co.uk/2017/01/31/nhs_reply_all_email...
A handful people replied to the entire company w/o realizing it - stuff like "Well I'm in California, I don't have to worry about it. Ha!".
I think it would have ended there. But some grumpy programmer in NYC of course decided to reply "People. Stop replying-all!" One would think being a programmer he'd be smart enough to reply to just the people who had unintentionally spammed the whole company. But no. He spammed the whole company.
And after that it was on. Dozens of emails a minute. Tons of replies like "Please take me off this list." Tons more grumpy people complaining. Big bosses pulling rank "Ok I am Vice President of muckety muck and we need to stop this replying all right now!" And the best: "Stop replying all to everyone to tell them to stop replying all!" - replied to all of course. O_o
It didn't help that a lot of people worked in labs and shared computers. So they'd log on and see a ton of emails w/o knowing what happened. By the end of the week it finally died down. Then the next Monday people came back from vacation, saw 500+ emails, and of course asked to be taken off the list. This went on for weeks before it finally trickled to a halt.
Why anyone was allowed to spam the entire company, or the address couldn't be blocked, I have no idea. I was tempted to use it to fish for a tennis partner. And then apologize and claim ignorance of course.