利用ASP.net编写发送Email程序

 WriteToStream(ref nwstream, "EHLO " + smtpHost + "\r\n");
 string welcomeMsg = ReadFromStream(ref nwstream);

 // implement HELO command if EHLO is unrecognized.
 if (IsUnknownCommand(welcomeMsg))
 {
  WriteToStream(ref nwstream, "HELO " + smtpHost + "\r\n");
 }
 CheckForError(welcomeMsg, ReplyConstants.OK);   

 // Authentication is used if the u/p are supplied
 AuthLogin(ref nwstream);

 WriteToStream(ref nwstream, "MAIL FROM: <" + msg.From.Address + ">\r\n");
 CheckForError(ReadFromStream(ref nwstream), ReplyConstants.OK);

 SendRecipientList(ref nwstream, msg.To);
 SendRecipientList(ref nwstream, msg.CC);
 SendRecipientList(ref nwstream, msg.BCC);

 WriteToStream(ref nwstream, "DATA\r\n");
 CheckForError(ReadFromStream(ref nwstream), ReplyConstants.START_INPUT);

 if (msg.ReplyTo.Name != null && msg.ReplyTo.Name.Length != 0)
  { WriteToStream(ref nwstream, "Reply-To: \"" + msg.ReplyTo.Name + "\" <" +
   msg.ReplyTo.Address + ">\r\n"); }
 else
  { WriteToStream(ref nwstream, "Reply-To: <" + msg.ReplyTo.Address + ">\r\n"); }
 
 if (msg.From.Name != null && msg.From.Name.Length != 0)
  { WriteToStream(ref nwstream, "From: \"" + msg.From.Name + "\" <" +
   msg.From.Address + ">\r\n"); }
 else
  { WriteToStream(ref nwstream, "From: <" + msg.From.Address + ">\r\n"); }
 
 WriteToStream(ref nwstream, "To: " + CreateAddressList(msg.To) + "\r\n");
 
 if (msg.CC.Count != 0)
  { WriteToStream(ref nwstream, "CC: " + CreateAddressList(msg.CC) + "\r\n"); }

 WriteToStream(ref nwstream, "Subject: " + msg.Subject + "\r\n");

 if (msg.Priority != null)
 { WriteToStream(ref nwstream, "X-Priority: " + msg.Priority + "\r\n"); }

 if (msg.Headers.Count > 0)
 {
  SendHeaders(ref nwstream, msg);
 }
 
 if (msg.Attachments.Count > 0 || msg.HtmlBody != null)
 {
  SendMessageBody(ref nwstream, msg);
 }
 else
 {
  WriteToStream(ref nwstream, msg.Body + "\r\n");
 }
 
 WriteToStream(ref nwstream, "\r\n.\r\n");
 CheckForError(ReadFromStream(ref nwstream), ReplyConstants.OK);
 WriteToStream(ref nwstream, "QUIT\r\n");
 CheckForError(ReadFromStream(ref nwstream), ReplyConstants.QUIT);
 CloseConnection();
}

private bool AuthLogin(ref NetworkStream nwstream)
{
if (username != null && username.Length > 0 && password != null && password.Length > 0)
{
 WriteToStream(ref nwstream, "AUTH LOGIN\r\n");
 if (AuthImplemented(ReadFromStream(ref nwstream)))
 {
  WriteToStream(ref nwstream, Convert.ToBase64String(
    Encoding.ASCII.GetBytes(this.username.ToCharArray())) + "\r\n");
  CheckForError(ReadFromStream(ref nwstream), ReplyConstants.SERVER_CHALLENGE);
  WriteToStream(ref nwstream, Convert.ToBase64String(Encoding.ASCII.GetBytes(
      this.password.ToCharArray())) + "\r\n");
  CheckForError(ReadFromStream(ref nwstream), ReplyConstants.AUTH_SUCCESSFUL);
  return true;
 }
}
return false;
}