Some Fridays (once a month?) were casual dress days where you could wear jeans instead of slacks (this was the distant past, when most professional workplaces still had real dress codes). This was an IT/Eng-wide thing, so we'd get an email reminder about this from an admin person in the department.
One time, I thought it would be funny to send my own email announcing pants-less Friday. So I took a copy of the email this admin sent and adjusted it accordingly. I did of course specify that you still had to wear underwear. I'm not a monster. Because I had programmer privileges in Notes, I was able to forge the sender so that it appeared to come from the department admin person, not me.
I _meant_ to send it to the small email group for just the other tech support folks (around 15 people or so). But I accidentally (?) sent it to all of IT/Eng, around 200-300 people, IIRC. Oops.
Needless to say, my boss's phone started ringing off the hook. I immediately went over to tell him what I'd done. He wasn't pleased, but I didn't get fired. I did have to write an apology email.
Of course, many folks in the department later told me it was the funniest thing they'd ever seen happen.
Soon after, I moved to programming at a different company. I think this was a good thing for many reasons, but one reason is that it was more challenging, so I wasn't bored with time on my hands to do stupid things like send prank emails to my coworkers.
At my previous job they had been using Notes since the company was founded in the early 90’s, meaning they lived through it being Lotus Notes, then IBM Notes and now HCL Notes.
Everything was deeply entrenched - email, warehouse inventory, ERP system, all documentation made in the entire company… just everything.
And this is for a scandinavian company manufacturing high tech devices for telecom and aviation, among other things.
It was… an interesting nightmare, constantly got in the way of any sort of productivity. Definitely contributed to me leaving early