I was working with a user who had Windows 8 and Office 2010 installed. The user had Start8 installed as the Windows 8 interface stinks. The user often ran searches via clicking Start and then typing search terms and hitting "See More Results" just like you can/could do in Windows 7. When clicking "See More Results" - the results included emails from Outlook. This was the critical behavior we wanted to keep (getting emails in the search results).
You'd get to the needed searches like this:
I upgraded the user's laptop to match our current software setup - Windows 10 and Office 2013. For this executive user, I also installed Start10 (not part of my standard install).
The bright side was that the user could still click on "see more results" and get files or emails, but the problem was that the user would double click on the emails and get nothing (no error or ability to see the message). I'm 95% sure I could have fixed the problem right then and there via deleting the file C:\Program Files\Common Files\System\MSMAPI\1033\MSMAPI32.DLL - but I wasn't sure about that fix until later. You can delete that MSMAPI32.DLL file with Outlook closed and the file Outlook will recreate the file on next open (credit for that info here).
My assumption was that the indexing was broken. The search was pulling up indexed results that didn't point to the underlying issue. I rebuilt the index. No dice. Same problem. I could see the searches, but the user could not double click on the emails and get Outlook to open them.
I then upgraded to Office (and Outlook 2016) assuming that it was some way in that Windows 10 was having trouble talking to Outlook 2013. With installation of Outlook 2016, emails would not appear in the "see more results" entries. I later learned that Microsoft says they have disabled the feature that made Outlook results appear in Windows searches. Supposedly, MS disabled this feature for both Outlook 2013 and Outlook 2016, but my experience says that Outlook 2013 still works.
If I could go back in time, I'd reinstall Outlook 2013, but in this case - I uninstalled Outlook 2016 and installed Outlook 2010. I had to delete the OST and let the OST rebuild. While I was at it, I rebuilt the index for best info for the user.
Things are great, right? Not true. I run a search, and I get emails among the search results, but I get an error of "Either there is no default mail client or the current mail client cannot fulfill the messaging request. Please run Microsoft Outlook and set it as the default mail client." I tried the MS FixIt and deleting the registry entries for both 32 bit and 64 bit as described in the excellent troubleshooting steps here:
However, no dice. I also tried to set Outlook as the default program via Set Program Defaults in Windows 10. No dice. The eventual fix was to delete C:\Program Files\Common Files\System\MSMAPI\1033\MSMAPI32.DLL with Outlook closed. Upon Outlook reopen, the file recreated itself (different size and date) and the ability to click on emails found in search was successful.