Don't mind me, just writing maintainable, legible, commented and documented code. What's that, an email validation? Let me just
/^(([^<>()\[\]\.,;:\s@\"]+(\.[^<>()\[\]\.,;:\s@\"]+)*)|(\".+\"))@(([^<>()[\]\.,;:\s@\"]+\.)+[^<>()[\]\.,;:\s@\"]{2,})$/i

RFC 5322 standard (yes that's an actual thing) is

(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*|"(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])*")@(?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\[(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?|[a-z0-9-]*[a-z0-9]:(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21-\x5a\x53-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])+)\])

Your keyboard just puked

@Verstrahlter why don't you allow subdomains? i@send.nud.es wouldn't be possible with yours if im correct

@gitreflog wait you mean that block of text means something? /s

@DeveloperACE come on. Thats one of the most readable regexes i ever saw?

@gitreflog Oh wow, actually after trying just a little bit, it is not hard to read at all! I just saw so many symbols, I gave up without trying... Anyway, wouldn't it be easier to specify the allowed chars, instead of the opposite? (I guess it would make it more clear)

Email validation should be far simpler. If the email has an @ and at least one . in it, let it be.

@monr0e Does not even have to have a dot technically

Great Talk on the matter of validating E-Mail-Addresses:

https://youtu.be/xxX81WmXjPg

Or just set the input type to email and set it as required, and let HTML5 do the work.

Email validation is best done by sending an actual email.

Email addresses are not parsable by regular expressions. Please never even try, it has long been proven to be impossible.