Outlook search in "classic" mode is inherently broken.  Try toggling to the "New" mode to see if the search suddenly works for new messages. At best, you can try to "re-index" Spotlight. There's many examples on the Internet for turn it on/off, deleting the Index cache and re-creating it, etc. First check the status of Spotlight's indexing: sudo mdutil -sav If a particular volume is disabled, commonly /System/Volumes/Data, you can enable it with: sudo mdutil -i on /System/Volumes/Data Or you can just enable everything with: sudo mdutil -ai on Check the status again with the first command and let indexing complete, then see if your search works.