TIL in 1997, a Reply All storm took down all of Microsoft's internal Exchange system
It started off with an employee sending an email to a distribution list called "Bedlam DL3" asking to be taken off the list. With 13,000 recipients and everyone replying all with, "Me too!" and other messages, it was estimated that over 15 million messages were sent through the system in an hour. This crashed the MTA service due to a recipient limit. Each time the MTA service recovered, it would attempt to resend the message again which lead to a crash loop.
As a result of the incident, the Exchange team introduced message recipient limits and distribution list restrictions to Exchange, which is something we all use today!
I love this story. We have preventive measures in place because of chaos like this. Back in the early 2010s I was doing a VA internship at my college's Veterans Affairs office. We would help other veteran students manage their GI Bill and other VA benefits as well as communicate events for our student vet community. The school used a student veteran distribution list just like this story but for a much smaller group of users.
One day the college's VA office sent out an email that a prominent anti war vet was coming to speak at the college which sparked a lot of controversy apparently with a good portion of the members of that DL. So much so that a reply all chain began and my student email inbox was blowing up from all the outrage. If I remember correctly, the event was ultimately canceled because so many student veterans were complaining.
Not all vets have seen combat, even if they have deployed. But aside from that most of these vets were early 20s that did one enlistment and are fresh out of active, so their life experience up until that point was high school to military to college. Not all of them, but a significant amount. That being said, even at the time I would've found the absurd response funny, except it meant more work for me that week to draft communication on behalf of the office.