To send emails using telnet, follow the below steps.
1. In the command prompt, use the code "telnet example.com 25" to connect.
2. Now type the code "ehlo example.com".
3. Type the from and to email addresses using the codes "mail from: firstname.lastname@example.org" and "rcpt to: email@example.com, firstname.lastname@example.org"
4. Type data along with subject and message to compose the message. To end the message, put a period on a line and then click Enter to send the email. It will look like,
Subject: My Telnet Test Email
This is an email sent by using the telnet command.
Note: when you are done, type quit to exit telnet.