Same issue here. Tried deleting and reinstalling outlook, tried sudo - rebuilding entire index directory in Terminal, tried adding/removing Mac HD in Spotlight privacy settings, tried adding/removing email accounts in Outlook. The issue appears to be related directly with Spotlight, not Outlook. Go figure, Apple can't seem to release an OS update that doesn't have a major issue. It's almost as if they don't even Beta test before release. Can't remember the last time I've installed a successful OSX update that didn't have major issues. Must have been when Steve was still around.

Same exact issue here. Tried rebuilding index directory completely, via Terminal. Tried to activate Spotlight function on/off via Terminal. Tried to delete/add email accounts in Outlook. Tried wiping Microsoft office completely and reinstalling. Tried add/remove Mac HD to privacy list in Spotlight preferences. Nothing works. Apple's OS updates are literally abysmal. They are disastrous every single time, and they can't seem to learn. Ever since Steve Jobs went, OS quality has steadily declined. The Big Sur update literally fried my Fusion drive and they had to replace it. I honestly can't understand how simple tasks like this fly under the radar during Beta testing. Either that, or they simply ignore these issues. Apart from Spotlight completely breaking, there are a number of Midi/driver issues as well. Shaking my damn head Apple get it together.

Where's Apple? Why are they completely silent on this topic? Incredibly frustrating