I’m of the opinion that all you should validate is that there is an @, the text to the right side (of the final @) is a well-formed dotted DNS domain, and that

I’m of the opinion that all you should validate is that there is an @, the text to the right side (of the final @) is a well-formed dotted DNS domain, and that there exists at least one (non-whitespace) character to the left of the (final) @. Yes, I can craft garbage emails that pass this quite easily, but who cares? If I’m crafting fake emails I can make valid ones too. This rule ensures I typed the @ and the dot in my domain (we really don’t need to support dotless email domains and it’s better to catch “foo@gmailcom”) and it won’t reject all the weird random emails people might have.