发送邮件时的附件怎么写的！

给你看一个邮件的例子，下面的内容就是你在smtp的data命令后要发的内容：From: 
To: 
Subject: 
Date: Fri, 14 Jun 2002 10:59:15 +0800
MIME-Version: 1.0
Content-Type: multipart/mixed;
boundary="----=_NextPart_000_005F_01C21392.860A9A70"
X-Priority: 3
X-MSMail-Priority: Normal
X-Mailer: Microsoft Outlook Express 5.50.4133.2400
X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4133.2400This is a multi-part message in MIME format.------=_NextPart_000_005F_01C21392.860A9A70
Content-Type: multipart/alternative;
boundary="----=_NextPart_001_0060_01C21392.860C2110"
------=_NextPart_001_0060_01C21392.860C2110
Content-Type: text/plain;
charset="gb2312"
Content-Transfer-Encoding: base64tPO80rrDo6ENCg0KICAgINXiysfO0tC0tcTSu7fdudjT2s34udjM5c+1veG5ubXEzNbC26GjDQoN
Cs31v6ENCg==------=_NextPart_001_0060_01C21392.860C2110
Content-Type: text/html;
charset="gb2312"
Content-Transfer-Encoding: base64PCFET0NUWVBFIEhUTUwgUFVCTElDICItLy9XM0MvL0RURCBIVE1MIDQuMCBUcmFuc2l0aW9uYWwv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------=_NextPart_001_0060_01C21392.860C2110--------=_NextPart_000_005F_01C21392.860A9A70
Content-Type: text/plain;
name="attach.txt"
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
filename="attach.txt"xNrN4rT6wO21xL3hubkNCsTazeK0+sDttcS94bm5DQrE2s3itPrA7bXEveG5uQ0KxNrN4rT6wO21
xL3hubkNCsTazeK0+sDttcS94bm5DQrE2s3itPrA7bXEveG5uQ0K------=_NextPart_000_005F_01C21392.860A9A70--上面的例子中：
Content-Type: text/plain;
name="attach.txt"
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
filename="attach.txt"Content-Type指示你的附件内容的MIME类型，如果附件为纯文本，就使用text/plain，如果为html格式，就使用text/html。其他内容类型你可以参考MIME的参考资料。Content-Transfer-Encoding: base64表明你的附件必须是经过base64编码的。在生成附件时，读取你的附件文件内容，然后进行编码。将编码后的文件内容紧接在上述内容之后。Content-Disposition: attachment; <- 代表附件内容的开始
filename="attach.txt" <- 附件文件名为：attach.txt。