In the unlikely event the Spotlight index is corrupted, you may have to go the extra mile getting the feature to re-index messages. One of the possible reasons is that Spotlight hasn’t yet indexed your data if you have recently added a new profile to Outlook for Mac. It’s hard to say why exactly this adverse situation might occur, but it makes some emails slip under the radar when you run a search. If so, the Mac’s Spotlight feature is blocked from searching that location. Outlook profile is listed in Spotlight’s Privacy tab.If it’s different, you may run into hurdles looking for personal correspondence in mail folders.
If you are using Microsoft Outlook 2016 for Mac or newer (which is the most plausible scenario), the valid path of the folder named “Outlook 15 Profiles” that stores profile information is as follows: ~/Library/Group Containers/UBF8T346G9.Office/Outlook.