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!
More on the story here:
https://techcommunity.microsoft.com/t5/exchange-team-blog/me-too/ba-p/610643
cross-posted from: https://techy.news/post/2224
Microsoft has a track record of having excellent uptime! /s
I find it somewhat funny that this article came out on the day Microsoft 365 had an outage for most of the day.