Trouble finding messages using Search in Outlook for Mac
Problem
You are unable to find messages in Outlook for Mac that you know exist in your email account.
Environment
- Outlook for Mac 365 and above
- Mac OS 10.13 and above
Solution 1
Make sure you have the desired search location of your email account selected (see image below). In Outlook, you have the option to Search in:
- Current Folder
- Subfolders
- Current Mailbox
- All Mail
- All Items
NOTE: Search with 'All Mail' or 'All Items' will take longer to complete than the other options

Solution 2
Email message need to be associated with Outlook for Mac, and Spotlight needs to be re-indexed for Outlook for Mac.
Please use the instructions the following address to do so:
https://support.microsoft.com/en-us/office/search-in-outlook-for-mac-returns-limited-or-no-results-for-macos-big-sur-b5dec081-3aa0-4f10-bba7-7a18f3f85252
Open Outlook and wait around 30 minutes. Then, test by searching for items that you could not find earlier.