Yesterday we had installed the Telnet client on our Windows Vista. Today, let’s try to send an email using nothing but the Telnet client. This is a very good way to troubleshoot problems in sending emails in your email client such as Microsoft Outlook, and while at the same time you can learn the protocols which actually happen in the background when you press the “send” button in your email client.
What I listed below is the general commands that will work on most mail servers. If yours do not work, you will need to check what’s the mail server you are currently running and change the commands slightly.
- Go to a DOS prompt
- Type “telnet”, hit Enter.
- Type “open mail.YourDomain.com 25” (replace YourDomain.com with your domain name. And replace the default port 25 if necessary), hit Enter.
- Type “HELO”, hit Enter.
- Type “AUTH LOGIN”, hit Enter.
Your telnet window should look like the following now.

Now, you now need to enter your full email address and then your password encoded in BASE64. To convert your full email address and your password to BASE64, you can use this handy BASE64 encoding tool. Enter your email, click on “Encode”, copy that encoded value in the telnet session and press Enter. After that do the same for your password.
Continue reading “SMTP authentication and send emails using Telnet”