There is a bug in the EmailHelper SendAsync method. If there is no mail server configured, often the case using IIS express in dev environments, the when calling smtp.Send() it will throw an error and cause the server to crash.

At present the method looks like this:

private static void SendAsync(object o)
        {
            SmtpClient smtp = ((dynamic)o).smtp;
            MailMessage message = ((dynamic)o).message;
            smtp.Send(message);
        }

The revised version should look like this:

private static void SendAsync(object o)
        {
            SmtpClient smtp = ((dynamic)o).smtp;
            MailMessage message = ((dynamic)o).message;

            try
            {
                smtp.Send(message);
            }
            catch (Exception ex)
            {
                // log exception here!
                Log.Add(LogTypes.Error, -1, ex.Message);
            }


        }

This will fix the issue.