All of a sudden when I try to open Outlook I get an error message that it cannot open the OST file and when I click OK the error message closes without opening the app. I tried follow other instructions for earlier versions - for example deleting the OST file reference. But when I try to open again the file is recreated but still cannot be opened (get the error message again). As far as I know between the last access to Outlook and now, no changes or updates were made to my Office programs.
UPDATE: On reboot, Outlook now opens and shows my email/Exchange account (an outlook.com address) but does not find any emails. When checking the folder with OST files, I see a new file was created (*** Email address is removed for privacy ***(3).ost) which is much smaller than the two previous filed created over two months ago. The previous 2 versions were about 170 MB, and this one created today - appended (3) - is only about 16 MB.