Regular expression for email

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What is the best regular expression for validating email addresses?

I tried the reg expression

^([a-zA-Z0-9_.-])+@([a-zA-Z0-9_.-])+\.([a-zA-Z])+([a-zA-Z])+

for the email validation.

Since I want the user to allow submitting even with the empty email address. So I changed the reg ex to

(^([a-zA-Z0-9_.-])+@([a-zA-Z0-9_.-])+\.([a-zA-Z])+([a-zA-Z])+)?

But this expression accepts any email address without any validation.

Your expression will accept anything because it can match the empty string (the ? meaning zero or one times) and every string "contains" the matching string. You want to compare the whole string, so put ^at the beginning and $ at the end - this way nothing BUT your regex can occur in the string. So either it is empty OR the complete pattern. — Konerak, May 25 '10 at 13:07

score 3 · Accepted Answer · answered May 25 '10 at 13:50

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Thanks Konerak!!!! I changed the expression to

^(([a-zA-Z0-9_.-])+@([a-zA-Z0-9_.-])+\.([a-zA-Z])+([a-zA-Z])+)?$

and this is working for me.

answered May 25 '10 at 13:50

Mohammad Nadeem

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And what about the + character? – Sean Kinsey May 25 '10 at 14:11
isn't underscore forbidden in host names? – Marcel Aug 27 '18 at 13:16

score 1 · Answer 2 · answered May 25 '10 at 12:46

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Welcome. http://www.ex-parrot.com/pdw/Mail-RFC822-Address.html

answered May 25 '10 at 12:46

miku

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I think this is unrealistic because RFC822 includes a lot of legacy address types that are rarely needed or supported by current software. – kervin May 25 '10 at 13:13
yeah, this is not practical. far better is this, and the discussion around it: http://www.regular-expressions.info/email.html – Richard H May 25 '10 at 14:17

score 1 · Answer 3 · edited Dec 10 '11 at 00:20

A good bit of info on doing this is available at this page.

As that page will tell you, it's extremely difficult to pass any and all RFC822-compliant addresses with a regex. You need to ask yourself just how important this is to your application.

Personally I would recommend, if applicable, simply asking users to enter the email address twice and then confirm with a confirmation email. That way you don't run the risk of erroneously rejecting a valid email address (an extremely annoying situation for users which will likely lose your site some customers).

score 1 · Answer 4 · answered May 25 '10 at 13:08

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How to: Verify That Strings Are in Valid E-Mail Format

answered May 25 '10 at 13:08

volody

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Regular expression for email

4 Answers4