Thanks for raising it. It is a difficult issue. It is bette to solve it. Jiankang Yao From: Arnt Gulbrandsen via UA-EAI Date: 2023-04-26 20:18 To: ua-eai@icann.org Subject: [UA-EAI] Email address syntax Hi, I promised to write something about email address syntax. It’s actually a touch more complicated than I mentioned yesterday. As John says, Email addresses are more complicated than one usually sees, and there exist syntax features that can be used to confuse people. But, I think, three reduced grammars: One might say that banning all the obs- productions in RFC5322 produces a reduced grammar. Those productions are obsolete, that’s why they’re called obs-whatever, and should not be used. Noone uses them anyway, I’m only mentioning this for completeness. The WHATWG HTML specification contains a simple grammar, which web browsers implement. Since one must expect email addresses to be typed into HTML forms, IMO following this specification is strongly advisable. The spec is on https://html.spec.whatwg.org/multipage/input.html#email-state-(type=email) and so far isn’t UA-ready. I fear that getting that UA-ready will shortly be one of my tasks. \X+ is an extremely simple PCRE (a regular expression) that IMO should match all addresses. I suspect we’ll see that in some well-known web software in the near future. IMO it’s safe to advise anyone to use only addresses that match the WHATWG spec (when extended) and also match \X+. The two suggestions complement each other; “ “@example.com matches \X+ but I’m not brave enough to use that an address like that -- Arnt Gulbrandsen UA Technology Sr. Manager, ICANN +32 492 374706
