“An attempt was made to access a socket in a way f

Question

I am trying to send an SMTP email when certain values in database crosses its threshold value.

I have already allowed ports 25,587 and 465 in the Windows firewall and disabled the option of preventing mass mail in the Antivirus. The code I am using is given below

using System.Net;
using System.Net.Mail;
using System.Net.Security;
using System.Security.Cryptography.X509Certificates;

 MailMessage mailMsg = new MailMessage();
        mailMsg.To.Add("[e-mail]");
        // From
        MailAddress mailAddress = new MailAddress("[e-mail]");
        mailMsg.From = mailAddress;


        // Subject and Body
        mailMsg.Subject = "MCAS Alert";
        mailMsg.Body = "Parameter out of range";


        SmtpClient smtpClient = new SmtpClient("smtp.servername.com", 25);
        smtpClient.UseDefaultCredentials = false;
        smtpClient.Timeout = 30000;
        System.Net.NetworkCredential credentials =
           new System.Net.NetworkCredential("username", "passwrod");
        smtpClient.Credentials = credentials;
        smtpClient.EnableSsl = true;
        //ServicePointManager.ServerCertificateValidationCallback = delegate(object s, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors) { return true; };
        smtpClient.Send(mailMsg);

Stack Trace

[SocketException (0x271d): An attempt was made to access a socket in a way forbidden by its access permissions xx.xx.xx.xx:25]
   System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress) +208
   System.Net.ServicePoint.ConnectSocketInternal(Boolean connectFailure, Socket s4, Socket s6, Socket& socket, IPAddress& address, ConnectSocketState state, IAsyncResult asyncResult, Exception& exception) +464

[WebException: Unable to connect to the remote server]
   System.Net.ServicePoint.GetConnection(PooledStream PooledStream, Object owner, Boolean async, IPAddress& address, Socket& abortSocket, Socket& abortSocket6) +6486360
   System.Net.PooledStream.Activate(Object owningObject, Boolean async, GeneralAsyncDelegate asyncCallback) +307
   System.Net.PooledStream.Activate(Object owningObject, GeneralAsyncDelegate asyncCallback) +19
   System.Net.ConnectionPool.GetConnection(Object owningObject, GeneralAsyncDelegate asyncCallback, Int32 creationTimeout) +324
   System.Net.Mail.SmtpConnection.GetConnection(ServicePoint servicePoint) +141
   System.Net.Mail.SmtpTransport.GetConnection(ServicePoint servicePoint) +170
   System.Net.Mail.SmtpClient.GetConnection() +44
   System.Net.Mail.SmtpClient.Send(MailMessage message) +1554

[SmtpException: Failure sending mail.]
   System.Net.Mail.SmtpClient.Send(MailMessage message) +1906
   Admin_Alert.SMTPAuth() in c:\Users\spandya\Documents\Visual Studio 2012\WebSites\WebSite3\Admin\Alert.aspx.cs:61
   Admin_Alert.Page_Load(Object sender, EventArgs e) in c:\Users\spandya\Documents\Visual Studio 2012\WebSites\WebSite3\Admin\Alert.aspx.cs:22
   System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +51
   System.Web.UI.Control.OnLoad(EventArgs e) +92
   System.Web.UI.Control.LoadRecursive() +54
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +772

What else I am missing here? Firewall inbound rules are there for these specific port addresses.

Answer 1

I had a same issue. It was working fine on the local machine but it had issues on the server. I have changed the SMTP setting. It works fine for me.

If you're using GoDaddy Plesk Hosting, use the following SMTP details.

Host = relay-hosting.secureserver.net
Port = 25 

Answer 2

Windows Firewall was creating this error for me. SMTP was trying to post to GMAIL at port 587. Adding port 587 to the Outbound rule [Outbound HTTP/SMTP/RDP] resolved the issue.

Answer 3

Please confirm that your firewall is allowing outbound traffic and that you are not being blocked by antivirus software.

I received the same issue and the culprit was antivirus software.

Answer 4

Ok, so very important to realize the implications here.

Docs say that SSL over 465 is NOT supported in SmtpClient.

Seems like you have no choice but to use STARTTLS which may not be supported by your mail host. You may have to use a different library if your host requires use of SSL over 465.

Quoted from http://msdn.microsoft.com/en-us/library/system.net.mail.smtpclient.enablessl(v=vs.110).aspx

The SmtpClient class only supports the SMTP Service Extension for Secure SMTP over Transport Layer Security as defined in RFC 3207. In this mode, the SMTP session begins on an unencrypted channel, then a STARTTLS command is issued by the client to the server to switch to secure communication using SSL. See RFC 3207 published by the Internet Engineering Task Force (IETF) for more information.

An alternate connection method is where an SSL session is established up front before any protocol commands are sent. This connection method is sometimes called SMTP/SSL, SMTP over SSL, or SMTPS and by default uses port 465. This alternate connection method using SSL is not currently supported.

Answer 5

If the other answers don't work you can check if something else is using the port with netstat:

netstat -ano | findstr <your port number>

If nothing is already using it, the port might be excluded, try this command to see if the range is blocked by something else:

netsh interface ipv4 show excludedportrange protocol=tcp

Answer 6

I got this error:

System.Net.Sockets.SocketException: An attempt was made to access a socket in a way forbidden by its access permissions

when the port was used by another program.