Here is how to send email using Telnet

1. Open the cmd prompt.
2. Type telnet server.com 25 (where “server.com” is the name of the smtp (outgoing) server of your email provider, such as smtp-server.austin.rr.com). This can be found by checking your account info in the program you normally use for email.
3. Type HELO server.com.
4. Type MAIL FROM: you@server.com.
5. You may get a message saying “250 ok”
6. Type RCPT TO: Friend1@anotherserver.com, friend_two@someotherserver.org, friend.3three@Someserver.com, etc.
7. again, You may get a message saying “250 ok”
8. To write the message, type DATA, followed by your message.
9. To end the message, put a period on a new line by itself and press Enter.
10. Type QUIT to exit Telnet. 

Got this info over at wikihow.com