add to web.config

  <system.net>
    <mailSettings>
      <smtp from="[email protected]">
        <network host="smtp.sendgrid.net" userName="u@d" password="p" />
      </smtp>
    </mailSettings>
  </system.net>

mail.cs

using System.Net.Mail;

// ..

private async Task configSendGridasync(IdentityMessage message)
{
    var myMessage = new MailMessage();
    myMessage.To.Add(new MailAddress(message.Destination));
    myMessage.From = new MailAddress("[email protected]", "test Support");
    myMessage.Subject = message.Subject;
    myMessage.IsBodyHtml = true;
    myMessage.Body = message.Body;
    
    var smtpClient = new SmtpClient();
    try
    {
        await smtpClient.SendMailAsync(myMessage);
    } catch(Exception ex)
    {
        Trace.TraceError(ex.Message + " SendGrid probably not configured correctly.");
    }
}