In our environment today we faced the strange issues in MAC Outlook 15.8. When I open the outlook its not showing in the main window and I can see the outlook preferences accounts settings.
When I research in the Microsoft community I found the solution. Please find the solution below
Delete the following folders in Macintosh HD ▸ Users ▸ <username> ▸ Library
This deletes all the user related information in outlook. All email accounts and local storage deleted.
After this, I ran “defaults delete com.microsoft.Outlook” once more and restarted Outlook 15.8 – this time it worked, but beware, you start from scratch losing all account info and locally stored emails. for runiing this
Open the Terminal app (usually found in Launchpad ▸ Other) and on the command line type: “defaults delete com.microsoft.Outlook” (without quotation marks) followed by Enter.
But after re-downloading all emails from the server, Outlook works again.
Access hidden user library files | Mac OS 10.7 and later
In the Finder, choose Go > Go To Folder.
In the Go To Folder dialog, type ~/Library
Hold down the Alt (Option) key when using the Go menu. The user library folder is listed below the current user’s home directory.
Note: After you open the Library folder, you can drag the Library icon from the top of that window to the Dock, Side Bar, or toolbar. That way, it’s readily accessible.
The following method makes the user library folder permanently visible.
Note: Adobe recommends that only advanced users use this method.
Note: The System administrator password is not visible as you type it.
Close Terminal for this change to take effect.
Courtsey- Microsoft Community
Microsoft Community for Outlook for mac 15.8