It's just to illustrate that the standard is more complicated than people might realise. I think you'll have problems getting most systems to accept an email ad

It's just to illustrate that the standard is more complicated than people might realise. I think you'll have problems getting most systems to accept an email address with two @s in it, but I might be wrong. Either way it would definitely break some (not too well written) code. Though if possible I'd err on the side of being too permissive rather than too restrictive. In the end the only true way to validate an address is to send it an email.