Years ago at the company I was working for an E-mail went out to “all users” by mistake. When people starting hitting the “Reply all” button it crashed our servers nation wide. It went on for several days.
My favorite mass emailing was when one disgruntled HR employee sent everyone in the company the full list of salaries with individual names.
The chaos caused was legendary—and the person fessed up and quit.
He had gotten his revenge on his bosses.