Perhaps worth adding that verifying an e-mail address via regex is difficult and not actually that useful.

Difficult, because a lot of e-mail addresses are syntactically valid. For example, a@b is valid. As is a@1.2.3.4. As is "spaces are cool 😎"@b (with the quotes).

And it's not that useful, because you need to send out an e-mail either way, if you want to know that it's the correct address and the user has access to it. A regex can't catch a typo in the actual words, for example.

If you want a basic sanity check to catch when the user types their name into the e-mail field, then you can require that it contains an @ and, if you want, that there's at least one symbol before and after.
If you go beyond that, you either need a massive regex or you're going to lock out users with unusual e-mail addresses.