telnet mail.server.com 25
EHLO mail.server.com
AUTH LOGIN
<base64-encoded-username>
<base64-encoded-password>
MAIL FROM: <user@server.com>
RCPT TO: <user@server.com>
DATA
From: <user@server.com>
To: <user@server.com>
Subject: Hello dear user

This is the mail body here.

.

# Dot ends the session and put's the mail into mail que