Convert non-ascii domain to SMTP compatible

When customers enter email addresses with non-ascii chars like开发者_如何学Go äüö our SMTP rejects to process them.

So I think might be there is a solution to handle those domains myself and convert them to punyocode.

Is there a simple way of doing so using c#?

Would this work anyway?

You can use Uri.DnsSafeHost to convert to Punycode:

using System;

class Test
{
    static void Main()
    {
        Console.WriteLine(ConvertToPunycode("caf\u00e9.com"));
    }

    static string ConvertToPunycode(string domain)
    {
        Uri uri = new Uri("http://"+domain);
        return uri.DnsSafeHost;
    }
}

In app.config:

<configuration>
  <uri>
    <idn enabled="All" />
  </uri>
</configuration>

Result:

xn--caf-dma.com

The problem with this approach is that you'll be changing the email addresses.

The email addresses bevan@example.com and bevän@example.com are different email addresses, however much they appear the same.

Making the change you suggest will break email - people might receive the messages, but they won't be able to reply to them.

Your SMTP server that doesn't handle accented characters sounds like a dinosaur. Much as it might be a pain in the proverbial, replacement and/or upgrade is likely the best solution.

You'll likely be able to get more appropriate assistance over on ServerFault.

Converting Unicode characters in your email address' domain name to Punycode resolves the correct DNS records so it won't be rejected by your SMTP. It can be done simply using System.Uri without modifying app.config:

/// <summary>
/// Try passing example@äüö.com
/// </summary>
/// <param name="email"></param>
/// <returns></returns>
internal string GetSafeEmail(string email)
{
    const char at = '@';
    string[] split = email.Split(at);
    string safeHost = new Uri("http://" + split[1]).IdnHost;
    // Don't convert the username to Punycode
    return string.Join(at, split[0], safeHost);
}