Question

I have Windows XP and configured SMTP server in my IIS. Specified AllUnAssigned in IP address of general tab and specified 127.0.0.1 in connection under Access tab.

Now I tried sending mails using my local SMTP server using the following code,

MailMessage amessage = new MailMessage();
amessage.To.Add(new MailAddress("[e-mail]"));
amessage.From = new MailAddress("[e-mail]");
amessage.Subject = "TestMail";
amessage.Body = "This is a testmail";
SmtpClient clienta = new SmtpClient("localhost");
clienta.Timeout = 500;
clienta.Credentials = CredentialCache.DefaultNetworkCredentials;
try
{
    clienta.Send(amessage);
}
catch (Exception ex)
{

   Console.WriteLine(ex);
    Console.ReadLine();
}

Console.ReadLine();

I don’t get any error in executing the above code but no mails were sent/received. When I checked in the Inetpub I find the below file:

From: postmaster@munged
To: [e-mail]
Date: Tue, 26 Apr 2011 11:07:22 +0530
MIME-Version: 1.0
Content-Type: multipart/report;
report-type=delivery-status;
boundary=”9B095B5ADSN=_01CC03D260FE2C6C00000003munged?xxx”
Message-ID:

Subject: Delivery Status Notification
(Failure)

This is a MIME-formatted message.
Portions of this message may be
unreadable without a MIME-capable mail
program.

–9B095B5ADSN=_01CC03D260FE2C6C00000003munged?munged
Content-Type: text/plain;
charset=unicode-1-1-utf-7

This is an automatically generated
Delivery Status Notification.

Delivery to the following recipients
failed.

   [e-mail]

–9B095B5ADSN=_01CC03D260FE2C6C00000003munged?munged
Content-Type: message/delivery-status

Reporting-MTA: dns;munged
Received-From-MTA: dns;munged
Arrival-Date: Tue, 26 Apr 2011
11:07:16 +0530

Final-Recipient: rfc822;[e-mail]
Action: failed Status: 5.0.0
Diagnostic-Code: smtp;550-5.7.1
[122.178.191.78] The IP you’re using
to send mail is not authorized to
550-5.7.1 send email directly to our
servers. Please use the SMTP relay at
your 550-5.7.1 service provider
instead. Learn more at
550 5.7.1
http://mail.google.com/support/bin/answer.py?answer=10336
m9si19863225wfl.114

–9B095B5ADSN=_01CC03D260FE2C6C00000003munged?munged
Content-Type: message/rfc822

Received: from munged
([127.0.0.1]) by munged with
Microsoft SMTPSVC(6.0.2600.2180);
Tue, 26 Apr 2011 11:07:16 +0530
MIME-Version: 1.0 From: [e-mail]
To: [e-mail] Date: 26 Apr 2011
11:07:16 +0530 Subject: TestMail
Content-Type: text/plain;
charset=us-ascii
Content-Transfer-Encoding:
quoted-printable Return-Path:
[e-mail] Message-ID:

X-OriginalArrivalTime: 26 Apr 2011
05:37:16.0515 (UTC)
FILETIME=[009D2330:01CC03D4]

This is a testmail

–9B095B5ADSN=_01CC03D260FE2C6C00000003munged?munged–

Can anyone please help me on this?

Answer 1

Here’s the important part of the error message:

Diagnostic-Code: smtp;550-5.7.1 [122.178.191.78] The IP you’re using to send mail is not authorized to 550-5.7.1 send email directly to our servers. Please use the SMTP relay at your 550-5.7.1 service provider instead.

To solve this, you’ll need to setup an SMTP relay to send to your ISP’s email servers. They’ll send to Google for you.

For clarity:

• This is NOT an application/code/C# problem, but an IIS problem.
• Google will NOT accept SMTP connections from random nodes on the internet. That means: YOUR Windows XP SMTP server will not have direct sending ability.
• You MUST send to a known good whitelisted SMTP host.
• Your best option is to configure IIS to act as a relay to a known good SMTP server.
• Your best bet for a known good SMTP server is your ISP’s. This is likely smtp.yourISP.com.
• This tutorial’s Steps 2 & 3 will help you achieve this. Your ‘smart host’ will be your ISP’s SMTP server DNS name or IP address.