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Asked: 2026-05-22T02:13:44+00:00

Possible Duplicates: Email Validation – Regular Expression What is the best regular expression for

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Possible Duplicates:
Email Validation – Regular Expression
What is the best regular expression for validating email addresses?

Hi All,

I have an email address roughly like this,

firstname.lastname@4domain.co.nz

Which doesn’t work with the regex I have here for email addresses. It doesn’t seem to like the 4 at the start of the domain.

private const string MatchEmailPattern =
        @"^(([\w-]+\.)+[\w-]+|([a-zA-Z]{1}|[\w-]{2,}))@" +
        @"((([0-1]?[0-9]{1,2}|25[0-5]|2[0-4][0-9])\.([0-1]?[0-9]{1,2}|25[0-5]|2[0-4][0-9])\." +
        @"([0-1]?[0-9]{1,2}|25[0-5]|2[0-4][0-9])\.([0-1]?[0-9]{1,2}|25[0-5]|2[0-4][0-9])){1}|" +
        @"([a-zA-Z]+[\w-]+\.)+[a-zA-Z]{2,4})$";

Most other corner cases work well with this regex, all of the below are rejected,

        Assert.IsFalse(EmailValidator.IsValidEmailAddress("..@test.com"));
        Assert.IsFalse(EmailValidator.IsValidEmailAddress(".a@test.com"));
        Assert.IsFalse(EmailValidator.IsValidEmailAddress(".@s.dd"));
        Assert.IsFalse(EmailValidator.IsValidEmailAddress("ab@988.120.150.10"));
        Assert.IsFalse(EmailValidator.IsValidEmailAddress("ab@120.256.256.120"));
        Assert.IsFalse(EmailValidator.IsValidEmailAddress("2@bde.cc"));
        Assert.IsFalse(EmailValidator.IsValidEmailAddress("-@bde.cc"));
        Assert.IsFalse(EmailValidator.IsValidEmailAddress("..@bde.cc"));
        Assert.IsFalse(EmailValidator.IsValidEmailAddress("_@bde.cc"));

Any other regexes people can suggest for emails that will work with the above?

Also the above regex has the advantage that it works with addresses like this, and a lot of them don’t,

firstname.lastname_@gmail.com

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1 Answer

  1. Editorial Team

    You should use the MailAddress class, like this:

    try {
    address = new MailAddress(address).Address;
} catch(FormatException) {
    //address is invalid
}

    If you use this approach to validate the e-mail address, be aware, that this MailAddress accepts the display name part of the e-mail address as well, and that may be not exactly what you want to achieve. For example, it accepts this strings as valid e-mail addresses:

    In these cases only the last part of the strings is parsed as the address, the rest before that is the display name. To get a plain e-mail address without any display name, you should check if the DisplayName property of the MailAddress instance is empty.

    bool isValid = false;

try
{
    MailAddress address = new MailAddress(emailAddress);
    isValid = (string.IsNullOrEmpty(address.DisplayName));
    // or
    //isValid = ((address.User + "@" + address.Host) == emailAddress);
}
catch (FormatException)
{
    //address is invalid
}

    Furthermore an address having a dot at the end, like “user@company.” is accepted by MailAddress either.

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