Valid and invalid email addresses from https://en.wikipedia.org/wiki/Email_address#Examples
simple@example.com
very.common@example.com
disposable.style.email.with+symbol@example.com
other.email-with-hyphen@example.com
fully-qualified-domain@example.com
user.name+tag+sorting@example.com (may go to user.name@example.com inbox depending on mail server)
x@example.com (one-letter local-part)
example-indeed@strange-example.com
admin@mailserver1 (local domain name with no TLD, although ICANN highly discourages dotless email addresses)
example@s.example (see the List of Internet top-level domains)
" "@example.org (space between the quotes)
"john..doe"@example.org (quoted double dot)
Abc.example.com (no @ character)
A@b@c@example.com (only one @ is allowed outside quotation marks)
a"b(c)d,e:f;g<h>i[j\k]l@example.com (none of the special characters in this local-part are allowed outside quotation marks)
just"not"right@example.com (quoted strings must be dot separated or the only element making up the local-part)
this is"not\allowed@example.com (spaces, quotes, and backslashes may only exist when within quoted strings and preceded by a backslash)
this\ still\"not\\allowed@example.com (even if escaped (preceded by a backslash), spaces, quotes, and backslashes must still be contained by quotes)
1234567890123456789012345678901234567890123456789012345678901234+x@example.com (local part is longer than 64 characters)
john..doe@example.com (double dot before @)
john.doe@example..com (double dot after @)