undeliverable email troubleshooting

Question

I am using IIS6 smtp to send emails out, some of these emails are coming back with the following error.

Could not deliver the message in the time limit specified. Please retry or contact your administrator.

What steps do I need to take to track done where the problem is? I currently believe the problem is either with my configuration or with the configuration of the mail server I am trying to send to.

Additional - Emails to this address work fine from a different address and emails from this address to other email address work to, so know it is something unique to this mail server combination

Thanks

Answer 1

MXToolbox is a great site for easily troubleshooting (some of) this stuff. Just type in the email host name (everything after the @ in the email address) and it'll show you who their MX server is. Then, click "SMTP Test" next to the result, and the site will automatically connect to their mail server to make sure it's up. If MXToolbox shows multiple MX servers, test them all in order.

If that passes, then you know the remote server is up, so that narrows down the problem to mail server configuration (either yours or theirs). You can use telnet to send an email manually through their server, and if it goes through, the problem is probably on your own server.

If you've never sent an email via telnet before, I recommend practicing on your own server first. Basically, you're going to telnet to port 25 on the SMTP server and type in commands, and the server will respond with numeric status codes and hopefully human-readable explanations, like this (your commands in bold, server responses in italics):

HELO myhostname.com
250 yourhostname.com Hello
MAIL FROM: me@myhostname.com
250 Sender ok
RCPT TO: you@yourhostname.com
250 recipient ok
DATA
250 enter your message
Subject: Test email

This is the body of the email. It ends when I type a period on a line by itself.
.
250 message sent
QUIT
220 Goodbye

Answer 2

not familiar with IIS but the logs don't say what happened on the remote end? I think the error you mention is what the end user sees so your logs should have something more detailed

Answer 3

Well, first find out what mailserver IIS is trying to deliver to (you may have to crank up the logging level to see this).

Then go from there: Maybe IIS is delivering to the wrong mailserver? Maybe the MX record for the recipient is not correct? Maybe the receiving mailserver is really down?