System.Net.Mail.SmtpException

My webserver does not have smtp on it but I'm still able to relay email to my email server with user name and password, my first question is that the dotnet is using an API that's built into server to relay?

Also email stopped working a day ago with error messageSyntax error, command unrecognized. The server response was: 5.1.0 Dropping connection due to an error on this server . Could this error be caused by the internal process dotnet uses to relay not working?

The 5.1.0 error is usually on the remote SMTP server and the error is propogated back to you. Does the server you relay to allow relays?

You're not relaying. System.Net.Mail simply sends the message to the defined SMTP server. Your error is a SMTP error, check the logs on the SMTP server to see what is happening, if you can. A 5.1.0 is a Sender Denied error, which most likely means you now need to use authentication. Checkwww.systemnetmail.com for help and samples.

Jeff

Still not getting this working getting, any help would be appreciated.

System.Net.Sockets.SocketException: No connection could be made because the target machine actively refused it

Line 88: try
Line 89: {
Line 90: client.Send(message);
Line 91: Response.Redirect("RequestAccepted.aspx");
Line 92: }
Source File:d:\Inetpub\KPClient\ContactUS.aspx.cs Line:90

Stack Trace:

[SocketException (0x274d): No connection could be made because the target machine actively refused it] System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress) +1001874 System.Net.Sockets.Socket.InternalConnect(EndPoint remoteEP) +33 System.Net.ServicePoint.ConnectSocketInternal(Boolean connectFailure, Socket s4, Socket s6, Socket& socket, IPAddress& address, ConnectSocketState state, IAsyncResult asyncResult, Int32 timeout, Exception& exception) +431[WebException: Unable to connect to the remote server] System.Net.ServicePoint.GetConnection(PooledStream PooledStream, Object owner, Boolean async, IPAddress& address, Socket& abortSocket, Socket& abortSocket6, Int32 timeout) +1447464 System.Net.PooledStream.Activate(Object owningObject, Boolean async, Int32 timeout, GeneralAsyncDelegate asyncCallback) +190 System.Net.PooledStream.Activate(Object owningObject, GeneralAsyncDelegate asyncCallback) +21 System.Net.ConnectionPool.GetConnection(Object owningObject, GeneralAsyncDelegate asyncCallback, Int32 creationTimeout) +318 System.Net.Mail.SmtpConnection.GetConnection(String host, Int32 port) +227 System.Net.Mail.SmtpTransport.GetConnection(String host, Int32 port) +316 System.Net.Mail.SmtpClient.GetConnection() +42 System.Net.Mail.SmtpClient.Send(MailMessage message) +1485

This turned out to be a bad router change that was not documented.