Email address regular expression

Question

I used the function below to validate email addresses.

// Function to test for valid email address.
        public static bool IsValidEmailAddress(String emailAddress)
        {
            Regex regex = new Regex(@"^[_a-zA-Z0-9-]+(\.[_a-zA-Z0-9-]+)*@[a-zA-Z0-9-]+(\.[a-zA-Z0-9-]+)*\.(([0-9]{1,3})|([a-zA-Z]{2,3})|(aero|coop|info|museum|name))$");
            Match match = regex.Match(emailAddress);
            return match.Success;
        }

This regular expression works for [e-mail], but not robert.o'[e-mail].

Can anyone help me to modify the regulation expression, making it to valid for robert.o'[e-mail]

Thanks in advance!

Answer 1

Read this as it discusses that very subject under the heading "Trade-Offs in Validating Email Addresses"

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John Grove - TFD Group, Senior Software Engineer, EI Division, http://www.tfdg.com

Answer 2

Email address validation is (IMHO) a worthless task! Check out the RFC standard. I suggest that you make sure you have [^@]+@.* that is the best one. Check out the forum post on why most regex's fail:

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

Phil Haacks comments:

I Knew How To Validate An Email Address Until I Read The RFC

and finally the RFC on wikipedia if you are still brave:

E-mail address

:-)

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William Wegerson (www.OmegaCoder.Com)

Answer 3

Below link will provide complete reference to solve your issue:

http://www.codeproject.com/KB/validation/Valid_Email_Addresses.aspx

Answer 4

Rohini,
I just tried the pattern you said was a "complete reference to solve" the issue.

string strRegex = @"^([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([a-zA-Z0-9\-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$";
Regex re = new Regex(strRegex);
if (re.Match("robert.o'[e-mail]").Success)
   Console.WriteLine("Success");

And it didn't match. I would listen to William's advice. He is an expert in Regex.

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John Grove - TFD Group, Senior Software Engineer, EI Division, http://www.tfdg.com

Answer 5

And it didn't match. I would listen to William's advice. He is an expert in Regex.

I do ok...but the thought is about the email pattern is that, if a user double validates the email address why question what they believe is the real one? Unless you are creating a new emaill address for a email box...what is the real point of true validation.... By simply checking for  characters before a @ sign and then a .ABC it should be a valid one.

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William Wegerson (www.OmegaCoder.Com)

Answer 6

Hi all,

in my company we use EmailVerify.NET (http://www.emailverify.net), a Microsoft .NET component which supports e-mail syntax checking, domain MX test and mailbox validation too.
E-mail validation up to the mailbox level is easy as writing the following code block:

var verifier = new EmailVerifier();
var result = verifier.Verify("[e-mail]", VerificationLevel.Mailbox);

if (result.IsSuccess)
{
   // Go on, send the message
}

Additional code samples can be found here.
From their home page:

EmailVerify.NET is a powerful .NET component which verifies email addresses using various techniques, including:

• Syntax verification, according to RFC 2821 and RFC 2822
• MX record lookup
• Disposable email address (DEA) validation
• SMTP availability check
• Mailbox existence check, with greylisting support
• Catch-all test

It is completely written in managed code (C#) and is compliant with the Common Language Specification (CLS), so it can be used with any other .NET language, including VB.NET, C++/CLI, J#, IronPython, IronRuby and F#.

The price for this component is very small (less than 50 bucks) and their support is one of the greatest I've ever found for a small software company like they are.
Hope this helps.