I have old version .net based project.

version is 4.5.2

Now I am trying to integrate Sendgrid to send email, but getting error. Below I am sharing code which I have tried and also error, if anyone can help me.

public void Email_ALL()
 {
     try
     {
         ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
         ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls11;

         var sendclient = new SendGridClient("api-key");
         var from = new EmailAddress("[email protected]", "Test");
         var subject = "Sending with Twilio SendGrid is Fun";
         var to = new EmailAddress("[email protected]", "Example User");
         var plainTextContent = "and easy to do anywhere, even with C#";
         var htmlContent = "<strong>and easy to do anywhere, even with C#</strong>";
         var msg = MailHelper.CreateSingleEmail(from, to, subject, plainTextContent, htmlContent);

         var result = Task.Run(() => sendclient.SendEmailAsync(msg)).GetAwaiter().GetResult();
     }
     catch (Exception ex)
     {
         throw ex;
     }
}

Error I am facing is below as well as I have attached screenshot.

System.Net.Http.HttpRequestException: 'An error occurred while sending the request.'

SocketException: An existing connection was forcibly closed by the remote host