When working on mail flow issues, one of the first troubleshooting steps with any mail server is to try and telnet into port 25 of the server. Exchange has an error, 530, that says that the smtp connection wasn’t authenticated. If you’re trying to relay through an Exchange server, that’s a good thing, as you wouldn’t want an open relay. However, if you’re trying to relay to an Exchange server, that’s not such a good thing. So let’s look at what this symptom looks like. First we try and telnet into port 25 of the server:
telnet exchange.krypted.com 25
Which shows the following:
Then we say hi:
And because the laws of robotics tell it to do so, the server says hi back:
250 exchange.krypted.com Hello
Then we try and relay to it:
And we get this error at some point in our smtp communication:
530 5.7.1 Client was not authenticated
Now, at this point we should look at the receive connector for Exchange, part of Hub Transport. To do so, open Exchange System Manager or Exchange Management Console and select Hub Transport under the Server Configuration section.
Here, locate your default receive connector (don’t do this on a send connector or you will create an open relay), right click it and then click on Properties.
At the Properties dialog, check the box for Anonymous users. This allows for another mail server to communicate with yours over smtp since that other server is basically just running through the message dialog we worked through earlier while telneted into the host. Click Apply to save the changes and for giggles go ahead and stop (disable) and start (enable) the connector.