你可以下载： http://download.csdn.net/detail/aa_qq110/3585719 看一下，这个程序是Linux的，但是很简单。 可以参考一下。 实质上就是： 1.先建立TCP连接 2按以下协议（即SMTP协议）发送邮件： S: 220 smtp.example.com ESMTP Postfix C: HELO relay.example.org S: 250 Hello relay.example.org, I am glad to meet you C: MAIL FROM:<[email protected]> S: 250 Ok C: RCPT TO:<[email protected]> S: 250 Ok C: RCPT TO:<[email protected]> S: 250 Ok C: DATA S: 354 End data with <CR><LF>.<CR><LF> C: From: "Bob Example" <[email protected]> C: To: "Alice Example" <[email protected]> C: Cc: [email protected] C: Date: Tue, 15 Jan 2008 16:02:43 -0500 C: Subject: Test message C: C: Hello Alice. C: This is a test message with 5 header fields and 4 lines in the message body. C: Your friend, C: Bob C: . S: 250 Ok: queued as 12345 C: QUIT S: 221 Bye {The server closes the connection}具体参考：http://en.wikipedia.org/wiki/Simple_Mail_Transfer_Protocol
http://download.csdn.net/detail/aa_qq110/3585719
看一下，这个程序是Linux的，但是很简单。
可以参考一下。
实质上就是：
1.先建立TCP连接
2按以下协议（即SMTP协议）发送邮件：
S: 220 smtp.example.com ESMTP Postfix
C: HELO relay.example.org
S: 250 Hello relay.example.org, I am glad to meet you
C: MAIL FROM:<[email protected]>
S: 250 Ok
C: RCPT TO:<[email protected]>
S: 250 Ok
C: RCPT TO:<[email protected]>
S: 250 Ok
C: DATA
S: 354 End data with <CR><LF>.<CR><LF>
C: From: "Bob Example" <[email protected]>
C: To: "Alice Example" <[email protected]>
C: Cc: [email protected]
C: Date: Tue, 15 Jan 2008 16:02:43 -0500
C: Subject: Test message
C:
C: Hello Alice.
C: This is a test message with 5 header fields and 4 lines in the message body.
C: Your friend,
C: Bob
C: .
S: 250 Ok: queued as 12345
C: QUIT
S: 221 Bye
{The server closes the connection}具体参考：http://en.wikipedia.org/wiki/Simple_Mail_Transfer_Protocol
有兴趣看看
http://download.csdn.net/detail/qq752923276/3233640
http://download.csdn.net/detail/jchen821214/1138229
然后再依次发送各种命令，自己查RFC文档，然后auth login
把base64加密的帐号和密码发过去。如果250就成功了
然后再写包头，正文。以及附件。完毕。