This is not really "validating" emails in the sense most people think of it. The RFC is about addressing SMTP envelopes, not entering email addresses. This woul

This is not really "validating" emails in the sense most people think of it. The RFC is about addressing SMTP envelopes, not entering email addresses. This would not be appropriate for e.g. checking if an address entered in a signup form is "valid." This includes a bunch of things that make no sense and aren't really email addresses (like embedded comments) and meanwhile has no idea that bogus@example.com is not an address that will actually receive mail. The only way to know an address is valid is to email it. It's mostly a joke. One might want to use this if writing a mail server, but even then...