When you open the Dynamics 365 App for Outlook on a Mac, you encounter the following error message:

“We’re sorry. It looks like the app isn’t installed for your Outlook mailbox. Please contact your system administrator.”


This error can be caused by stale data in the Outlook for Mac web browser cache.


Fully clear the cache using the following steps: 

  1. Start the Finder application 

  1. Hold the Option button down and then click the Go menu. The Library option should appear as one of the available options. 

  1. Click the Library menu option. The Library folder view will appear 

  1. Under the Library folder, locate the Containers folder and expand it. 

  1. Under the Containers folder, locate the com.MicrosoftOsfWebHost folder and expand it. 

  1. To clear the web browser cache, you must move the following to the Trash: 

  • com.Microsoft.OsfWebHost/Data/Library/Caches/com.Microsoft.OsfWebHost (whole folder) 

  • com.Microsoft.OsfWebHost/Data/Library/Cookies/Cookies.binarycookies (file) 

  1. Restart Outlook and restart the Dynamics 365 App for Outlook. 

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