The "valid e-mail address" definition doesn't accept IPv6 emails

[mgol]

The "valid e-mail address" definition in the spec:
https://html.spec.whatwg.org/#valid-e-mail-address
doesn't accept emails with an IPv6 host like xyz@[IPv6:2001::1]. E-mails like that are defined in "RFC 5321 (SMTP)" in section 4.1.3:
https://tools.ietf.org/html/rfc5321#section-4.1.3
We've got an issue in AngularJS about not supporting such e-mails:
angular/angular.js#16599
and I noticed the HTML standard doesn't do that either. Is it a conscious decision? If yes, what are the reasons?

I searched the issues & PRs but the word "IPv6" doesn't return any relevant results.

[annevk]

I somewhat doubt it was. Not supporting internationalized emails is: https://www.w3.org/Bugs/Public/show_bug.cgi?id=15489.

cc @tkent-google

[tkent-google]

I'm negative of supporting the IP address form of email addresses in the HTML platform.

• I guess many web applications don't support this form of email addresses.
• It's easy to make such element by <input type=text pattern=...>

[mgol]

I realize it's easy to use <input type=text pattern=...> but shouldn't the spec allow all valid emails to reduce surprises?

Just to note, the W3C spec allows such emails: w3c/html#1638 (comment)

[annevk]

Well, it was just argued that it could cause surprise.

We still need some kind of way to support internationalized email addresses at least, perhaps we should support IP addresses in that variant too. If it's opt-in than applications can decide for themselves whether they want to support it.

(It's not clear to me why the W3C decided to change this without implementer support.)

[gibson042]

It's easy to make such element by <input type=text pattern=...>

I believe it is technically possible to properly validate email addresses via regular expression, but I challenge anyone describing such a task as "easy" to attempt it. I'll happily provide counterexamples in response to any proposed pattern.