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Comment by rbranson | Hacker News Reader

I'm sure this will break a ridiculous number of regular expressions for email address validation.

Yes, but that is their own fault for trying to use a regex to validate email addresses. :)

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I wish people would stop posting that. Yes, that covers most (though not all) of the RFC definitions of what constitutes an email address, but in practice you only want to accept a tiny subset of those.

Curious: Why would you want to accept only a tiny subset of those? What do you gain by that?

Well, the really simple example is the string "postmaster". It is a perfectly legitimate email address, and almost always deliverable. But rarely something you want to actually accept.

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