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E-mail Address Validating Regular Expressions – a Warning

This page has been floating around in links over the past couple of weeks, as a collection of test cases to compare e-mail address validating regular expressions. However, watch out: it’s wrong.

RFC822/2822 defines an email address with a bare IP address domain part as using:

  domain-literal  =       [CFWS] "[" *([FWS] dcontent) [FWS] "]" [CFWS]

In other words, this test case is not valid at all:

  [email protected]

Instead, it should be:


ditto for the other addrs using IP addresses in the domain part. They’re rare, but the non-bracketed form is definitely not legal and should not be considered so in the test cases.

I sent a mail to the author a few days ago without response, hence this post.