Below are the instructions on how to test SMTP Auth using telnet:
- The first thing you need to do is get username and password in base64 encoding. Check this link for reference.
- Once you get base64 encoded username and passwords, now you need to connect to the mail server using telnet.
telnet mailserver.com 25
- Now after you get connected, greet the mail server.
- Now, we need to let the server know that you want to authenticate with it:
- The server should have returned
334 VXNlcm5hbWU6;this is a base64 encoded string asking you for your username, paste the base64 encoded username you created earlier.
- Now the server should have returned
334 UGFzc3dvcmQ6;Again this is a base64 encoded string now asking for your password, paste the base64 encoded password you created.
- Now you should have received a message telling you that you successfully authenticated. If it failed your user/pass may have been wrong or your mail server is broken.
Below is a log of successful SMTP AUTH connection over telnet:
[email protected] [~]# telnet exampledomain.com 25
Connected to exampledomain.com (18.104.22.168).
Escape character is '^]'.
220-server1.exampledomain.com ESMTP Exim 4.66 #1 Wed, 09 May 2007 23:55:12 +0200
220-We do not authorize the use of this system to transport unsolicited,
220 and/or bulk e-mail.
250-server1.exampledomain.com Hello [22.214.171.124]
250-AUTH PLAIN LOGIN
235 Authentication succeeded
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