C#实现发送邮件的问题,请高手指点啊

 这个恐怕控制不了，应该涉及到net基类对于协议的解释。下面是RFC3249中的一个例子，标红色的部分应该就是类似于你看到的文本附件了。Date: 14 Dec 1999 17:48:44 +0900
      From: [email protected]
      Message-ID: <[email protected]>
      Subject:  Your message was processed successfully. (MDN)
      To: [email protected]
      Mime-Version: 1.0
      Content-Type: multipart/report;
        report-type=disposition-notification; boundary="61FD1001_IFAX"      --61FD1001_IFAX
      Content-Type: text/plain      This is a Return Receipt for the mail that you sent to
      "[email protected]".  The message and attached files may
      have been printed, faxed or saved.  This is no guarantee that the
      message has been read or understood.
      --61FD1001_IFAX
      Content-Type: message/disposition-notification      Reporting-UA: ken-ifax.example.com; barmail 1999.10
      Original-Recipient: rfc822;[email protected]
      Final-Recipient: rfc822;[email protected]
      Original-Message-ID: <[email protected]>
      Disposition: automatic-action/MDN-sent-automatically; dispatched      --61FD1001_IFAX--