What is the correct regular expression for an email address?

Question

Duplicate: http://stackoverflow.com/questions/201323/what-is-the-best-regular-expression-for-validating-email-addresses

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There seem to be an awful lot of different variants on this on the web and was wondering if there is a definitive answer?

Preferably using the .net (Regex) dialog of regular expressions.

Answer 1

regular-expressions says that this one matches about 99%

[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?

Answer 2

Please see that one question.

Answer 3

I've had the same problem some time ago. RFC 2822 defines it and according to this page this one is useful and is the one i picked: "[a-z0-9!#$%&'+/=?^{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_{|}~-]+)*@(?:a-z0-9?.)+(?:[A-Z]{2}|com|org|net|gov|mil|biz|info|mobi|name|aero|jobs|museum)\b"

Answer 4

[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?

Probably want to add A-Z next to all the lower case versions in order to allow uppercase letters as well.

Answer 5

The definitive answer? Or the normal answer?

I ask because the formal email address specification allows all sorts of weird things (parenthesis, quoted phrases, etc) that most people don't bother to account for.

See this page for a list of both comprehensive and normal regex'es.

Answer 6

I don´t think there´s a silver bullet for email regex verification.

what people are commonly doing is to verify only for mistakes, like the absence of @ and one dot. And then send a email verification to that address. It´s the only way to be sure that they email is actually valid.

Answer 7

This question has been asked and answered several times:

http://stackoverflow.com/questions/201323/what-is-the-best-regular-expression-for-validating-email-addresses

http://stackoverflow.com/questions/211842/why-are-people-using-regexp-for-email-and-other-complex-validation

http://stackoverflow.com/questions/156430/regexp-recognition-of-email-address-hard

Specifically related to .NET:

http://stackoverflow.com/questions/369543/validating-e-mail-with-regular-expression-vb-net

Answer 8

Have a look here for a short answer. However this is something that is difficult to do 100% right with regular expressions. See here for details.

Answer 9

I don't know if there's one definitive answer for this one, but if you put aside actually checking if the domain exists, email addresses boil down to <username>@<domain>, where <domain> contains at least one dot and two to four characters in the suffix. You can do all kinds of things to check for illegal/special characters, but the simplest one would be:

^[\w-\.]+@([\w-]+\.)+[\w-]{2,4}$