I recently had an issue with Outlook 2021 and Outlook 365: Some of the favorites (located in the left pane on the top) were disappearing on Outlook restart. I found some suggested solutions to start outlook from the commend line: outlook.exe /resetnavpane. But that did not help in my case. What worked for me was to add the following Registry key and then restart Outlook: HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Autodiscover DWORD: ExcludeLastKnownGoodUrl Value: 1 Read more [...]