Test your SMTP email server – quick and easy using Telnet and Command Line!

One of the things I run into a lot as a System Administrator/Technical Services Engineer is troubleshooting email servers and systems, making sure they are set up correctly, etc. And one of the biggest issues is often having your email server incorrectly configured. 

Is your CRM instance not sending emails? Is it the CRM Email Router, or is it the Email server itself? What’s an easy way to tell?

Fortunately, Microsoft has a lot of built-in tools to help with that! Read on to see a quick and easy way to test your SMTP email server to make sure it is responding to email.

For this example, we’re going to use Telnet. Make sure it’s installed on whatever machine you are using to test (please note that it has to be a machine on the domain you are testing).

1.)   From this machine, open command prompt, then start a Telnet session: type telnet and…

Telnet Screenshot1

….Press Enter.

Telnet Screenshot2

2.)   Type o <your mail server’s domain> <your port number> and then press Enter.

Telnet Screenshot3

3.)   Type EHLO <your mail server’s domain> and then press Enter. You’ll get an output that looks something like the below.

Telnet Screenshot4

4.)   Type AUTH LOGIN, and the server will respond with an encrypted prompt for your username, then your password. (This step may be skipped if your mail server doesn’t require authentication, or allows anonymous authentication – for instance, if you are just working in a lab environment.)

5.)   Once that is entered, type MAIL FROM:<sender@domain.com> and press Enter. 

Telnet Screenshot5

6.)   Type RCPT TO:<recipient@otherdomain.com> and press Enter.

Telnet Screenshot6

7.)   Type DATA. At this point you can type message text if desired; when done, press Enter, type a period (.), then press Enter again.

8.)   If mail is configured and working properly, you will see a message similar to the below that says the mail is queued for delivery. (This mail won’t actually send, this is a simulation to test the connection only.)

Telnet Screenshot7

And that’s it! If you get any errors, you know that you need to troubleshoot your SMTP settings; if you do not, and you get a message similar to step 8, you know that your SMTP server is configured correctly.

For more information on troubleshooting Email and SMTP, check out Microsoft’s TechNet Article!

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