Unable to send email: An attempt was made to access a socket in a way forbidden...

This just started happening and I am not sure why... When I try to send an email via one of my Winhost email addresses, I get the error message, "An attempt was made to access a socket in a way forbidden by its access permissions [Server IP : Port #]."

Why would this have started happening all the sudden?

Code:

        private string smtpHost = "mail.myhost.com";
        private int smtpPort = 25;
        public const string NoReplyAddress = "[email protected]";
        public const string NoReplyUsername = "[email protected]";
        public const string NoReplyPassword = "MyPassword1";
        private bool enableSsl = false;

        private string errorMsg = "";

        public void sendEmail(string addrTo, string subject, string msg, string addrFrom = NoReplyAddress,
            string username = NoReplyUsername, string password = NoReplyPassword)
        {
            try
            {
                errorMsg = "";

                // Setup the mail message
                MailMessage mm = new MailMessage(addrFrom, addrTo);
                mm.Subject = subject;
                mm.Body = msg;
                mm.IsBodyHtml = true;
                mm.BodyEncoding = Encoding.Default;

                // Setup SMTP client
                SmtpClient smtp = new SmtpClient();
                smtp.Host = smtpHost;
                smtp.Port = smtpPort;
                smtp.EnableSsl = enableSsl;

                // Setup credentials
                NetworkCredential nc = new NetworkCredential();
                nc.UserName = username;
                nc.Password = password;
                smtp.UseDefaultCredentials = false;
                smtp.Credentials = nc;

                // Send the mail message
                smtp.Send(mm);

                // trigger Sent event
                //Sent(this, EventArgs.Empty);
            }
            catch (Exception ex)
            {
                errorMsg = ex.Message;

                // trigger Failed event
                //Failed(this, EventArgs.Empty);
            }
        }
    }

 

Nevermind. Problem solved.

I started using port 587 instead of 25; everything works now.