I could probably write a RegEx for email format validation that’s accurate, but why would I when there are ones already written and readily available that covers all possible legit variations on the standard? I never understood why people insist on writing their own (crap) RegEx for something with as many possible variations they can miss like email…
And that one isn’t even a weird edge case! It’s a domain with a sub domain, if they can’t even cover that case then it’s an extra shitty RegEx