Outlook 2016 and Mac OS incompatibility - multiple episodes of loss of search functionality Over the last year, I have needed to reinstall my 2016 Outlook account on my Macbook air multiple times and sometimes needed to do a repair on the indexing (more than a dozen times). It is constantly losing the search function.

I have macOS Mojave 10.14.6, and always upgrade OS and Outlook software when prompted. The problem seems to happen when there has been an update of macOS or of Outlook, but also just out of the blue for no apparent reason. I have spent multiple hours each time to resolve this. 

I last reinstalled my Outlook account a week ago, and already the indexing has been scrambled. It is not that no emails are found on a search, but just some of them and in no predictable way. 

From reading other postings, I am at a complete loss to understand how and why this problem has remained unfixed for so long by two of the world's largest companies to the detriment of Apple users. Is this really a highly complex problem? How can this be finally and comprehensively addressed?
Outlook searching relies on spotlight indexing.  I would start with ensuring that Sys Prefs - Spotlight - Privacy is empty.  You can rebuild the index with the below steps.  As a sidebar perhaps this is part of the reason why it's randomly losing results: https://eclecticlight.co/2019/08/02/spotlight-search-can-skip-files/

Open Terminal and run:

sudo mdutil -i off /
sudo mdutil -i on /
sudo mdutil -E