通过代理服务器发送邮件有点棘手，但最终通过使用代码通过套接字发送邮件解决了这个问题。
发布答案较晚，但假设它可能对其他人有帮助。
从链接的代码中获得帮助
附上下面的代码，SmtpServer对象与所描述的相同，
#region ..... SOCKET MAIL .....
private enum SMTPResponse : int
{
/// <summary>
/// 220
/// </summary>
CONNECT_SUCCESS = 220,
/// <summary>
/// 235
/// </summary>
CRED_SUCCESS = 235,
/// <summary>
/// 250
/// </summary>
GENERIC_SUCCESS = 250,
/// <summary>
/// 334
/// </summary>
AUTH_SUCCESS = 334,
/// <summary>
/// 354
/// </summary>
DATA_SUCCESS = 354,
/// <summary>
/// 221
/// </summary>
QUIT_SUCCESS = 221
}
public static string EncodeTo64(string toEncode)
{
byte[] toEncodeAsBytes = System.Text.Encoding.ASCII.GetBytes(toEncode);
string returnValue = System.Convert.ToBase64String(toEncodeAsBytes, Base64FormattingOptions.None);
return returnValue;
}
public bool SendFromSocket(MailMessage message)
{
var requestUri = new System.Uri("smtps://" +SmtpServer.Host +":"+SmtpServer.Port);
Uri proxy = null;
//This is magic code which does your job for the proxy
using (var web = new System.Net.WebClient())
{
proxy = web.Proxy.GetProxy(requestUri);
}
using (var s = new TcpClient(proxy.DnsSafeHost, proxy.Port ))
{
using (var stream = s.GetStream())
using (var clearTextReader = new StreamReader(stream))
using (var clearTextWriter = new StreamWriter(stream) { AutoFlush = true })
using (var sslStream = new SslStream(stream))
{
if (!Check_Response(clearTextReader, SMTPResponse.CONNECT_SUCCESS))
{
s.Close();
return false;
}
clearTextWriter.WriteLine("HELO");
if (!Check_Response(clearTextReader, SMTPResponse.GENERIC_SUCCESS))
{
s.Close();
return false;
}
clearTextWriter.WriteLine("STARTTLS");
if (!Check_Response(clearTextReader, SMTPResponse.CONNECT_SUCCESS))
{
s.Close();
return false;
}
sslStream.AuthenticateAsClient(SmtpServer.Host);
bool flag = sslStream.IsAuthenticated;
using (var reader = new StreamReader(sslStream))
using (var writer = new StreamWriter(sslStream) { AutoFlush = true })
{
writer.WriteLine(string.Format("EHLO {0}", SmtpServer.Host));
if (!Check_Response(reader, SMTPResponse.GENERIC_SUCCESS))
{
s.Close();
return false;
}
writer.WriteLine("AUTH LOGIN");
if (!Check_Response(reader, SMTPResponse.AUTH_SUCCESS))
{
s.Close();
return false;
}
writer.WriteLine(EncodeTo64(SenderId));
if (!Check_Response(reader, SMTPResponse.AUTH_SUCCESS))
{
s.Close();
return false;
}
writer.WriteLine(EncodeTo64(Password));
if (!Check_Response(reader, SMTPResponse.CRED_SUCCESS))
{
s.Close();
return false;
}
writer.WriteLine("MAIL FROM: <{0}>", message.From);
if (!Check_Response(reader, SMTPResponse.GENERIC_SUCCESS))
{
s.Close();
return false;
}
foreach (MailAddress To in message.To)
{
writer.WriteLine("RCPT TO: <{0}>", To.Address);
if (!Check_Response(reader, SMTPResponse.GENERIC_SUCCESS))
{
s.Close();
return false;
}
}
if (message.CC != null)
{
foreach (MailAddress cc in message.CC)
{
writer.WriteLine(string.Format("RCPT TO: <{0}>", cc.Address));
if (!Check_Response(reader, SMTPResponse.GENERIC_SUCCESS))
{
s.Close();
return false;
}
}
}
StringBuilder Header = new StringBuilder();
Header.Append("From: " + message.From + "\r\n");
Header.Append("To: ");
for (int i = 0; i < message.To.Count; i++)
{
Header.Append(i > 0 ? "," : "");
Header.Append(message.To[i].Address);
}
Header.Append("\r\n");
if (message.CC != null)
{
Header.Append("Cc: ");
for (int i = 0; i < message.CC.Count; i++)
{
Header.Append(i > 0 ? "," : "");
Header.Append(message.CC[i].Address);
}
Header.Append("\r\n");
}
Header.Append("Date: ");
Header.Append(DateTime.Now.ToString("ddd, d M y H:m:s z"));
Header.Append("\r\n");
Header.Append("Subject: " + message.Subject + "\r\n");
Header.Append("X-Mailer: SMTPDirect v1\r\n");
string MsgBody = message.Body;
if (!MsgBody.EndsWith("\r\n"))
MsgBody += "\r\n";
if (message.Attachments.Count > 0)
{
Header.Append("MIME-Version: 1.0\r\n");
Header.Append("Content-Type: multipart/mixed; boundary=unique-boundary-1\r\n");
Header.Append("\r\n");
Header.Append("This is a multi-part message in MIME format.\r\n");
StringBuilder sb = new StringBuilder();
sb.Append("--unique-boundary-1\r\n");
sb.Append("Content-Type: text/plain\r\n");
sb.Append("Content-Transfer-Encoding: 7Bit\r\n");
sb.Append("\r\n");
sb.Append(MsgBody + "\r\n");
sb.Append("\r\n");
foreach (object o in message.Attachments)
{
Attachment a = o as Attachment;
byte[] binaryData;
if (a != null)
{
//FileInfo f = new FileInfo(a.);
sb.Append("--unique-boundary-1\r\n");
sb.Append("Content-Type: application/octet-stream; file=" + a.Name + "\r\n");
sb.Append("Content-Transfer-Encoding: base64\r\n");
sb.Append("Content-Disposition: attachment; filename=" + a.Name + "\r\n");
sb.Append("\r\n");
Stream fs = a.ContentStream;
binaryData = new Byte[fs.Length];
long bytesRead = fs.Read(binaryData, 0, (int)fs.Length);
fs.Close();
string base64String = System.Convert.ToBase64String(binaryData, 0, binaryData.Length);
for (int i = 0; i < base64String.Length; )
{
int nextchunk = 100;
if (base64String.Length - (i + nextchunk) < 0)
nextchunk = base64String.Length - i;
sb.Append(base64String.Substring(i, nextchunk));
sb.Append("\r\n");
i += nextchunk;
}
sb.Append("\r\n");
}
}
MsgBody = sb.ToString();
}
writer.WriteLine("DATA\r\n");
if (!Check_Response(reader, SMTPResponse.DATA_SUCCESS))
{
s.Close();
return false;
}
Header.Append("\r\n");
Header.Append(MsgBody);
Header.Append(".\r\n");
Header.Append("\r\n");
Header.Append("\r\n");
writer.WriteLine(Header.ToString());
if (!Check_Response(reader, SMTPResponse.GENERIC_SUCCESS))
{
s.Close();
return false;
}
writer.WriteLine("QUIT\r\n");
Check_Response(reader, SMTPResponse.QUIT_SUCCESS);
s.Close();
return true;
}
}
}
}
private static bool Check_Response(StreamReader netStream, SMTPResponse response_expected)
{
int response;
int read = 0;
StringBuilder sResponse = new StringBuilder();
do
{
char[] buffer = new char[1024];
read = netStream.Read(buffer, 0, buffer.Length);
sResponse.Append(buffer);
}
while (read == 1024);
response = Convert.ToInt32(sResponse.ToString().Substring(0, 3));
if (response != (int)response_expected)
return false;
return true;
}
#endregion ..... SOCKET MAIL .....
