SMTP Mail Error->"Unable to connect to the remote server

Question

_{Friday, August 2, 2013 9:22 PM}

I've seen this problem everywhere searching...but haven't been able to resolve it.

• I have created a simple console application to test smtp on a WinXP Pro box.
• First I enabled port 25, then I just disabled the Windows firewall altogether.
• There is no McAffee installed that would block the port.

• I also attempted to telnet and was refused.
• I ping the mail server and it responds correctly

Here's the code sample..

static void Main(string[] args)
        {
            MailMessage msg = new MailMessage("[email protected]", "[email protected]", "test", "This is a test");

            SmtpClient client = new SmtpClient("smtp.domain.com");
System.Net.NetworkCredential("user", "pass");
System.Net.NetworkCredential cred = new NetworkCredential("user", "pass");
client.Credentials = CredentialCache.DefaultNetworkCredentials;
            
            try
            { client.Send(msg); }
            catch (SmtpException ex)
            { 
                Console.WriteLine(ex.ToString());
                Console.ReadKey();
            }

Here's the error it throws:

{System.Net.Mail.SmtpException: Failure sending mail. > System.Net.WebException: Unable to connect to the remote server > System.Net.Sockets.SocketException: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond 123.45.789.123:25
   at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress)
   at System.Net.Sockets.Socket.InternalConnect(EndPoint remoteEP)
   at System.Net.ServicePoint.ConnectSocketInternal(Boolean connectFailure, Socket s4, Socket s6, Socket& socket, IPAddress& address, ConnectSocketState state, IAsyncResult asyncResult, Int32 timeout, Exception& exception)
    End of inner exception stack trace 
   at System.Net.ServicePoint.GetConnection(PooledStream PooledStream, Object owner, Boolean async, IPAddress& address, Socket& abortSocket, Socket& abortSocket6, Int32 timeout)
   at System.Net.PooledStream.Activate(Object owningObject, Boolean async, Int32 timeout, GeneralAsyncDelegate asyncCallback)
   at System.Net.PooledStream.Activate(Object owningObject, GeneralAsyncDelegate asyncCallback)
   at System.Net.ConnectionPool.GetConnection(Object owningObject, GeneralAsyncDelegate asyncCallback, Int32 creationTimeout)
   at System.Net.Mail.SmtpConnection.GetConnection(String host, Int32 port)
   at System.Net.Mail.SmtpTransport.GetConnection(String host, Int32 port)
   at System.Net.Mail.SmtpClient.GetConnection()
   at System.Net.Mail.SmtpClient.Send(MailMessage message)
    End of inner exception stack trace 
   at System.Net.Mail.SmtpClient.Send(MailMessage message)
   at mailTest.Program.Main(String[] args) in C:\mailTest\mailTest\mailTest\Program.cs:line 25}

I'm at a loss.

thanks

All replies (7)

_{Tuesday, August 13, 2013 4:32 PM ✅Answered | 2 votes}

McAfee was blocking port 25.

Got admin rights and disabled mass emailing setting.

Thanks everyone.

_{Friday, August 2, 2013 9:50 PM | 1 vote}

If you cannot telnet to port 25 on smtp.domain.com, you will be unable to use smtp.domain.com to send mail.

Karl

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_{Saturday, August 3, 2013 11:52 PM}

Well, I opened that port up in the XP Firewall...

Shouldn't that have fixed the problem?

Also, I shut the firewall off altogether.

Thanks

Doug

_{Sunday, August 4, 2013 12:51 AM}

On whose side did you open Port 25? Client, Server or both?

As a test with Tellnet failed, this is clearly nto a programming issue. It is a server-administration issue.

Let's talk about MVVM: http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/b1a8bf14-4acd-4d77-9df8-bdb95b02dbe2 Please mark post as helpfull and answers respectively.

_{Sunday, August 4, 2013 3:09 AM}

I  find some threads which are similar with your question, you can refer to the below threads to get more help:

http://stackoverflow.com/questions/3238277/asp-net-smtpclient-unable-to-connect-to-the-remote-server

http://social.msdn.microsoft.com/Forums/vstudio/en-US/64c8e0e9-4c93-4d6b-bf11-87e0e0d2f2be/unable-to-connect-to-the-remote-server-while-trying-to-send-mail-in-win-app

http://stackoverflow.com/questions/5899180/sending-an-email-through-gmail-smtp-server-ssl

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_{Tuesday, April 26, 2016 4:22 PM}

McAfee VS Enterprise always gets me, too. Thank you.

_{Monday, July 27, 2020 11:42 AM}

I think this is a resource problem. you not dispose disposable object

try this code:

using(MailMessage msg = new MailMessage("[email protected]", "[email protected]", "test", "This is a test")){

            using(SmtpClient client = new SmtpClient("smtp.domain.com"))            {
                  System.Net.NetworkCredential("user", "pass");
                  System.Net.NetworkCredential cred = new NetworkCredential("user", "pass");
                  client.Credentials = CredentialCache.DefaultNetworkCredentials;
            
            try
            {                 client.Send(msg);                    }
            catch (SmtpException ex)
            { 
                Console.WriteLine(ex.ToString());
                Console.ReadKey();
            }     }}