We use SignalR for real-time updates to the client. If this is not working for you, I would suggest opening a ticket. This is something that will not be easy to debug especially with just bug reports on the community as it may require looking through the operating environment. Among a couple things make sure nothing else besides SmarterMail has port 50010 bound. We also have a custom build that contains enhanced logging.
You can see the bound port using this command, then matching up the PID to a service in Task Manager.
netstat -nao | find "50010"
Matt Petty
Senior Software Developer
SmarterTools Inc.
www.smartertools.com