网上的文章可能过于深入，不太适合新手看，这里介绍最简单的几条SMTP指令，仅需要输入很少的命令即可成功发送一封邮件。
其中粗体部分为输入的命令，蓝色部分为可变内容，灰色为服务器应答内容──
[root@localhost ~]# telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.localdomain (127.0.0.1).
Escape character is '^]'.
220 localhost.localdomain ESMTP Sendmail 8.13.8/8.13.8; Sun, 27 Sep 2009 20:02:18 +0800
HELO www.coelite.cn
250 localhost.localdomain Hello localhost.localdomain [127.0.0.1], pleased to meet you
MAIL from: moky@coelite.cn
250 2.1.0 moky@coelite.cn... Sender ok
RCPT TO: moky@chinabaiya.com
250 2.1.5 moky@chinabaiya.com... Recipient ok
RCPT TO: moky@vip.qq.com
250 2.1.5 moky@vip.qq.com... Recipient ok
DATA
354 Enter mail, end with "." on a line by itself
Subject: Hello
Content-Type: text/html
<html>
<body>
<a href="http://www.coelite.cn">coelite</a>
</body>
</html>
.
250 2.0.0 n8RC2IrV003529 Message accepted for delivery
QUIT
221 2.0.0 localhost.localdomain closing connection
Connection closed by foreign host.
