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Comment by oinksoft | Hacker News Reader

Practically, those W3C/WHATWG regexes probably are fine, but they aren't correct. For instance they fail to match the valid address c."@".t@gmail.com because they don't handle quoted strings correctly. I'd expect they also match some invalid addresses. My understanding was that only a Perl regex can test an address against the standard: http://www.ex-parrot.com/pdw/Mail-RFC822-Address.html

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It may be incorrect to reject that email, but it's good to reject that email.

Why reject a perfectly valid email? Why do you get to thumb your nose at that particular one?

It's only 'valid' because of the particular decisions made by someone writing a random RFC. There's next to no reason to allow quoted strings, and even less reason to allow a different character set inside of them.

Email addresses do not need escape sequences.

Doesn't this sort of RFC typically summarize and codify real-world usage, rather than coming up with new stuff? If a feature is in there, I'd have thought it's because somebody uses it.

At some point you just have to reach the level of "Yeah... don't do that." I would suspect have "@" as part of your email probably approaches that line.

It would be interesting to know the context. If this feature was already in a popular piece of software, then saying "don't do that" in your standard risks fragmenting things rather than codifying them, and that's no good either.

Where do you draw the line? I occasionally have valid GMail addresses with "+" in them rejected because someone wrote a crappy validator.

Allow all the characters that are supposed to be valid outside of quotation marks. Letters, numbers, .!#$%&'*+-/=?^_`{|}~

That way if you don't mind letting through double periods or domain segments having more than 63 characters, you can validate an email with two character classes separated by an @. The basic regex looks like [xx]+@[yy]+

> It's only 'valid' because of the particular decisions made by someone writing a random RFC.

You know that's exactly what "valid" means, when talking about something standardized, right?

In HTML there's no reason to use " outside of an attribute value. Should browsers reject it?

I don't think gmail will let you register that email address.

Okay then, c."@".t@someotherdomain.com

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