Ever set up a new receive connector in Exchange only to have your device completely fail at connecting to it? I have…

Lucky for you (and me!) it’s relatively simple to troubleshoot SMTP connections using Telnet, to see where exactly the connection is going wrong.

Troubleshooting SMTP Authentication using Telnet

1) Open a telnet tool on your mail server.
a) On most PC you can open a dos window and:
Enter “telnet”
Enter “set LOCAL_ECHO”
Enter “open mail.YourDomain.com 25” (replace YourDomain.com with your domain)
Enter “HELO”
Enter “AUTH LOGIN”

You now need to enter your email and then your password encoded in BASE64.

If you have successfully authenticated the server will return: “235 authenticated”

Enter “MAIL FROM YourUserName@YourDomain.com” (replace YourUserName@YourDomain.com with your email address)
Enter 
RCPT TO  DestinationEmail” (replace DestinationEmail with the destination email)
Enter “
DATA”
Enter “
Subject: Test using telnet”
Enter “”  (Send a blank line to separate the headers from the message body)
Enter “This is just a test to see if I can SMTP auth from my PC”
Enter “.”

The server will return: “250 Message queued”

Source: webpan.com


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