Rnaapp.exe
(Microsoft)
Windows Dial-Up Networking application. RNAAPP only appears in your Task List if your PC tries or tried to dial out at some stage, or if it is waiting for an inbound connection using Dial-Up Networking.
Recommendation :
Essential. Leave untouched. That said, if you are in the middle of troubleshooting Dial-Up networking problems, then do an "End Task" on it if you are not connected via Dial-Up Networking, and you may find that some of your problems disappear.