Attempting to use Exchange Web Services

Question

Hi, 

I am attempting to write a test application in c# that uses Exchange Web Services over TLS1.2 to connect the Exchange Server 2010 and send an email.

I have used the example downloaded from https://code.msdn.microsoft.com/Send-Email-with-Exchange-50189e57 as a starting point with minor changes to suit our Exchange configuration.

Our Exchange server is configured to use TLS 1.2

If I run the program from inside our domain it is successful but if I run it from outside then I get the following message:

Using dotnet 4.5

“The requested security protocol is not supported”

private void sendButton_Click(object sender, RoutedEventArgs e)
 {
     try
     {
         ExchangeService service = new ExchangeService(ExchangeVersion.Exchange2010_SP2);
         service.Url = new Uri(ExchangeServerURI);
         ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
         service.Credentials = new WebCredentials(MailUserName, MailPassword);

         EmailMessage message = new EmailMessage(service);
         message.Subject = subjectTextbox.Text;
         message.Body = bodyTextbox.Text;
         message.ToRecipients.Add(recipientTextbox.Text);
         message.Save();

         message.SendAndSaveCopy();

         System.Windows.MessageBox.Show("Message sent!");
     }
     catch(Exception ex)
     {
         MessageBox.Show(ex.Message);
     }
 }

Any help to get this working would be much appreciated,

Thanks,

John

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