h3r3tic is right. For practice though, try connecting to your ISP's SMTP server and sending the message from there. It should recognize you as a valid user and relay the mail for you. Assuming it does recognize you, this is what the session should look like. This is a session between me and my ISP's SMTP server. Addresses have been sanitized.

open xxx.xxx.xxx.xxx 25
Trying xxx.xxx.xxx.xxx...
Connected to smtp.domain.com
Escape character is '^]'.
220 smtp.domain.com ESMTP server (InterMail vM.5.01.06.05 201-253-122-130-105-20030824) ready Sun, 30 Nov 2003 16:02:09 -0500
helo upin.heaven
250 domain.com
MAIL FROM:<[email protected]>
250 Sender <[email protected]> Ok
RCPT TO:<[email protected]>
250 Recipient <[email protected]> Ok
DATA
354 Ok Send data ending with <CRLF>.<CRLF>
This is a test.
The quick brown fox jumps over the lazy dog.
.
250 Message received: [email protected]en
quit
221 smtp.domain.com ESMTP server closing connection
Connection closed by foreign host.

And the email I recieved looked like this:
Return-Path: <[email protected]>
Received: from upin.heaven ([xxx.xxx.xxx.xxx]) by smtp.domain.com (InterMail vM.5.01.06.05 201-253-122-130-105-20030824) with SMTP id <[email protected]> for <[email protected]>; Sun, 30 Nov 2003 16:10:19 -0500
Message-Id: <[email protected]>
Date: Sun, 30 Nov 2003 16:10:35 -0500


This is a test.
The quick brown fox jumps over the lazy dog.