I think it's impossible to actually write an email regex because addresses can have arbitrarily deeply nested escaping. I may have that wrong. I'd hope that regex would be .+@.+ and that's it (watch me get Cunninghammed because there is some valid address wherein those plusses should be stars).

TIL Cunningham's Law[0]. I knew about that phenomenon but not the proper name. Thanks!

[0] https://en.wikipedia.org/wiki/Ward_Cunningham#Law