What caused the Socket Exception while sending email from Console application?

Question

I'm trying to write a basic console app that will send an email. The problem is that I keep getting the Socket exception:

An attempt was made to access a socket in a way forbidden by its access permissions xxx.xxx.x.xxx:25

I turned off my windows firewall but it didn't change anything. I tried to run it with and without credentials specified. I also tried to use different smtp servers including smtp.mail.yahoo.com with port 25 and my credentials but with no luck. What is the problem causing this exception?

I'm running VS2008 on Windows 7. Below is my code sample and the exception I get.

static void Main(string[] args)
{
        String recipient = "[email protected]";
        String sender = "[email protected]";

        MailMessage message = new MailMessage();
        message.From = new MailAddress(sender);
        message.To.Add(new MailAddress(recipient));
        message.Subject = "Subject";
        message.Body = "Body";

        SmtpClient smtp = new SmtpClient
        {
            Host = "smtp.server",
            Port = 25,
            EnableSsl = true,
            DeliveryMethod = SmtpDeliveryMethod.Network,
            //UseDefaultCredentials = false,
            //Credentials = new NetworkCredential("validemail", "validpassword"),                
            Timeout = 3000
        };

        try
        {
            smtp.Send(message);
        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        }
    }

And the exception I got:

System.Net.Mail.SmtpException: Failure sending mail. ---> 
System.Net.WebException: Unable to connect to the remote server --->
System.Net.Sockets.SocketException: An attempt was made to access a socket in a way forbidden by its access permissions xxx.xxx.x.xxx:25
   at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress)
   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& abortSocket
6, 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.SmtpClient.Send(MailMessage message)
   --- End of inner exception stack trace ---
   at System.Net.Mail.SmtpClient.Send(MailMessage message)
   at ...Program.Main(String[] args) in ...\Program.cs:line xxx

Solution

I had very similar situation once and it turned out that the antivirus was just blocking that port. Your possible options are listed here: http://social.msdn.microsoft.com/Forums/br/transactsql/thread/c083c2c6-f74e-42cd-a811-4329ff7aa5f1

Comments

[anetafr]

I've checked that nothing is listening on that port. Once I test it on another machine I update the comment but I need to get home first to have another test machine.

[anetafr]

I've tried all possible combinations and nothing has changed, still the same exception.

[anetafr]

the status code is 10013. I've checked the meaning but I don't know how to solve the issue.

[anetafr]

EnableSSL needs to be set to false, otherwise there is a problem with authentication. On one machine, Avast warned me that SSL should be disabled, on the other I've just got Authentication Exception.

[Murtuza Kabul]

I assume that the certificate on your mail server is expired. There is a workaround for that, let me know if it is really so.