Well, and remember: If in doubt, send them an e-mail. You probably want to do that anyways to ensure they have access to that mailbox.
You can try to use a regex as a basic sanity check, so they’ve not accidentally typed a completely different info into there, but the e-mail standard allows so many wild mail addresses, that your basic sanity check might as well be whether they’ve typed an into there.
The regexes are written to comply with RFC 5332 and 6854
They are well defined and you can absolutely definitively check whether an address is allowable or not.
Yeah, I’m just saying that the benefit of using such a regex isn’t massive (unless you’re building a service which can’t send a mail).
a@b is a syntactically correct e-mail address. Most combinations of letters, an @-symbol and more letters will be syntactically correct, which is what most typos will look like. The regex will only catch fringe cases, such as a user accidentally hitting the spacebar.
And then, personally, I don’t feel like it’s worth pulling in one of those massive regexes (+ possibly a regex library) for most use-cases.
