Many of my usernames at my company are based on my email and it's pretty long - by the time you add the domain it's a good 47 characters...

I was at a Python conference once and met someone whose email ended '@boehringer-ingelheim.com'. That's 25 letters right there.

https://www.boehringer-ingelheim.com/media-stories/press-rel... has a camilla.krogh_lauritzen@boehringer-ingelheim.com at 48 characters, for example.