Select “Start“, then search for “Outbox” in the Start Searcharea. Exit out of Outlook or go to the “Send / Receive” tab and select “Work Offline“. Choose Apple menu, then System Preferences, and then Spotlight. If you are on macOS Mojave (10.14), you can follow the steps below to reindex Spotlight for Outlook for Mac. Due to some changes in macOS Mojave, this tool no longer works in 10.14 and higher. You will get the fastest help there and I think you will find the contributors more than helpful. Everyone there is a Mac user AND an Office user, something you can’t say about Apple’s forums.
As Office is not an Apple product, I strongly recommend asking in the Microsoft Office:Mac forums here: Office for Mac forums.
