Added a new Exchange account to Outlook 2016 the other day and when I ran Outlook it responded with:
“Cannot start Microsoft Outlook. Cannot open the Outlook window. The set of folders cannot be opened. The file C:\Users\xxx\AppData\Local\Microsodt\Outlook\firstname.lastname@example.org is not an Outlook data file(.ost).”
Some quick Googlephoo found this page on the Technet forums. The first fix resolved the problem.
1. Start Outlook with the switch “/resetnavpane”.
Press Win + R, type “outlook.exe /resetnavpane” in the Run window, press Enter.
This will recover the Navigation Pane configuration file, it works for some users in such scenario.
Restarted Outlook 2016 to be sure. No error occured.