Dave Burke - Freelance .NET Developer specializing in Online Communities

A freelance .NET Developer

SMTP Relaying with .NET 1.1

I've been wrestling with relaying .NET STMP messages beyond our local domain since around 3:00 this afternoon.  It's now around 5:30.  I know, it's a Friday, but darn it, when something doesn't work on one of my servers--whether that particular something is in use or not (and this happens to be not in use)--it bugs me and has to be fixed.

We all have CDO email procs and sometimes need to send to non-domain addresses.  My classic ASP CDO procs worked fine, and am quite certain my .NET 1.0 CDO proces did, but not .NET 1.1.  I knew it had something to do with .NET security, and tried impersonation, changing the username to SYSTEM in the machine.config, adding ASPNET to the SMTP admin group, etc.  Then I found the Golden Google Egg below.  

SmtpMail.SmtpServer = ""; // I had it pointing to the exchange server...

It makes perfect sense now.  You must use LOCALHOST as your smtpserver and let IT do the forwarding for you.

Ahhh, yes.  Now I can relax and enjoy my weekend.

Thank you Charles Fineblum!

From: Charles Fineblum (charle1@comcast.net)
Subject: Re: SMTP error: Could not access 'CDO.Message' object
Newsgroups: microsoft.public.dotnet.languages.csharp
Date: 2003-08-18 11:39:20 PST

Hi Chad:

"You need to use localhost and set the forwarding of your local SMTP server to your main mail router server"

By setting SmtpMail.SmtpServer = "", it should use local smtp server. How do I set forwarding to main mail server? I don't see this setting in SMTP props. I also tried adding the ASP.net account in security tab of SMTP prop, but still same error.

Thanks,
Charlie
Posted: Aug 30 2003, 12:31 AM by daveburke | with 6 comment(s)
Filed under:

Comments

Brian Desmond said:

I fail to see why this is required. So long as the SMTP virtual server on your Exchange box is configured to allow connections & relaying from the web server's IP, and it allows anonymous authentication, you're good to go. Check the authentication tab of the SMTP virtual server's properties. SMTP on Exchange is IIS.
# August 31, 2003 1:42 AM

Dave Burke said:

This is interesting, Brian. Thanks. My network admin partner handles configuration of the Exchange server and steps in with local server issues, but I will pass this along.
# August 31, 2003 9:51 AM

Steffen Grünwald said:

I´m glad to found this article. I read the SmtpServer from the Web.config file and set it there to "" (string.Empty) and it works fine.

Thanks a lot

Steffen

# November 25, 2003 4:18 AM

Paul B said:

I have an issue where I have IIS set up locally on my machine. I can send an email out via an exe. The issue occurs when I try to run the same code set though an ASP.NET project. It bombs out with the same error as above, even though I set the SMTP server to localhost. Any ideas?
# December 12, 2003 1:37 PM

Vlad said:

I got it working but. In my code I don't specify smtp server.

So I don't know which server its using behind the scene. How can I find out and where this configuration is? Is this a CDO configuration?

Many thanks!

                         MailMessage msgMail = new MailMessage();

msgMail.To = toperson;

msgMail.From = fromperson;

msgMail.Subject = emailsubject;

msgMail.BodyFormat = MailFormat.Html;

msgMail.Body = emailbody;

SmtpMail.Send(msgMail);

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