Issue happens when email is send from asp.net mvc 5 application hosted under iis/8.5
Sample web.config:
...
<system.net>
<mailSettings>
      <smtp from="noreply@smart-payment.ru" deliveryMethod="Network">
		    <network host="smtp.elasticemail.com" enableSsl="false" port="2525" userName="noreply@smart-payment.ru" password="d0774536-164a-4f59-b4bd-76511c50eb78" defaultCredentials="false" />
	    </smtp>
    </mailSettings>

Steps to reproduce:
 1. Configure <mailSettings> node within root asp.net Web.config

  2. Send email using System.Net.Mail.SmtpClient. Consider next sample code:

```cs
using System.Net.Mail;
...
public class Mailer {
public void SendMail(MailLetter message)
        {
using (var smtpClient = new SmtpClient())
            using (var msg = new MailMessage
            {
                IsBodyHtml = true,
                Subject = "Some Subject",
                Body = "Some body",
                From = new MailAddress(message.From, message.FromDisplayName)
            })
            {
                msg.ReplyToList.Add(new MailAddress(string.IsNullOrWhiteSpace(message.ReplyTo) ? message.From : message.ReplyTo, message.FromDisplayName));
                foreach (var addr in message.To)
                    msg.To.Add(new MailAddress(addr));
                smtpClient.Send(msg);
            }
}
...
}
```
Actual result:
Exception is thrown on `smtpClient.Send(msg)` invocation

```
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 188.165.1.80:2525
   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, Exception& exception)
```

Expected result: