Invalid email addresses
Abc.example.com (no @ character) PASS
A@b@c@example.com (only one @ is allowed outside quotation marks) PASS
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) PASS
just"not"right@example.com (quoted strings must be dot separated or the only element making up the local-part) PASS
this is"not\allowed@example.com (spaces, quotes, and backslashes may only exist when within quoted strings and preceded by a backslash) PASS
this\ still\"not\\allowed@example.com (even if escaped (preceded by a backslash), spaces, quotes, and backslashes must still be contained by quotes) PASS
1234567890123456789012345678901234567890123456789012345678901234+x@example.com (too long) FAIL
john..doe@example.com (double dot before @) FAIL
with caveat: Gmail lets this through, Email address#Local-part the dots altogether
john.doe@example..com (double dot after @) PASS