Validaiting emails with Net.Mail MailAddress

Question

I have read on SO about validating emails with MailAddress and have produced the folowing code:

    try
                    {
                        var address = new MailAddress(value.Email);
                    }
                    catch (FormatException)
                    {
                        emailError = "Invalid Email";

 }

To my great surprise the string ndskfndlfk@sdflsdf validates as good email. Any idea why is it so?

That might not be valid WWW domain name but on a private network I think it is a valid domain name. If you want to get more selective then Regex. — paparazzo, Sep 21 '12 at 22:14
Beware: do not go overboard on validating email addresses. Believe me, it's more hassle than it's worth. — Arran, Sep 21 '12 at 22:41
In case you are going to stay with that I posted as an answer. — paparazzo, Sep 21 '12 at 22:46
@Arran: Totally agree. If the email address is coming from a user registration, I just send a typical verification email with a confirmation link to the address in question. That way it not only validates the email address, but also verifies that it's real. — Spectre87, Sep 21 '12 at 22:46
It's valid everywhere, see the relevant RFCs. Also see newgtlds which will probably shake up some bad assumptions about host names. Note that you cannot reliably validate email addresses with regular expressions; see [this question](http://stackoverflow.com/a/201378) for more information. — tne, Jul 09 '14 at 10:50

score 1 · Accepted Answer · answered Sep 21 '12 at 22:38

If you really need to filter those email addresses, you could use the little utility found here, which uses Regex to validate email addresses. Note that this is the .Net 4.0 version - it's a little different for 4.5.

using System;
using System.Globalization;
using System.Text.RegularExpressions;

public class RegexUtilities
{
   bool invalid = false;

   public bool IsValidEmail(string strIn)
   {
       invalid = false;
       if (String.IsNullOrEmpty(strIn))
          return false;

       // Use IdnMapping class to convert Unicode domain names.
       strIn = Regex.Replace(strIn, @"(@)(.+)$", this.DomainMapper);
       if (invalid) 
          return false;

       // Return true if strIn is in valid e-mail format.
       return Regex.IsMatch(strIn, 
              @"^(?("")(""[^""]+?""@)|(([0-9a-z]((\.(?!\.))|[-!#\$%&'\*\+/=\?\^`\{\}\|~\w])*)(?<=[0-9a-z])@))" + 
              @"(?(\[)(\[(\d{1,3}\.){3}\d{1,3}\])|(([0-9a-z][-\w]*[0-9a-z]*\.)+[a-z0-9]{2,17}))$", 
              RegexOptions.IgnoreCase);
   }

   private string DomainMapper(Match match)
   {
      // IdnMapping class with default property values.
      IdnMapping idn = new IdnMapping();

      string domainName = match.Groups[2].Value;
      try {
         domainName = idn.GetAscii(domainName);
      }
      catch (ArgumentException) {
         invalid = true;      
      }      
      return match.Groups[1].Value + domainName;
   }
}

Otherwise, if it's for user registration, I usually just depend on email verification - i.e. the system sends the user an email with a link, and clicking the link therefore validates that the email address is real.

It is possible for a valid email address not to be a real one. In other words, it may even pass a perfect validation system, but that's no guarantee that it exists.

score 1 · Answer 2 · answered Sep 21 '12 at 22:50

That might not be valid WWW domain name but on a private network I think it is a valid domain name. If you want to get more selective then Regex.

I try and parse legit email (eliminate phony used by spam) using Regex and it is messy.

If you have access to the actual email header then it does not really get easier but it get more accurate.

Validaiting emails with Net.Mail MailAddress

2 Answers2