Using older versions of Outlook for Mac in business environments
Hi Steve7
You can refer to AI’s answer first for the detailed Spotlight indexing and search troubleshooting steps.
Regarding your additional point about Main Profile and Profile 2021, the Microsoft guidance explains how to use Outlook Profile Manager to view the available profile names, but it does not provide a separate documented method there to identify which of multiple profiles is currently being used. Microsoft notes that Main Profile is the default profile name, but with two existing profiles, it is best not to assume that this is necessarily the one containing your current Outlook data.
Troubleshoot search issues in Outlook for Mac | Microsoft Support
For that reason, it is best not to delete, rename, or otherwise modify either profile, or remove and re-add the IMAP account, until the profile containing the historical mail has been confirmed.
Since this is a business account (based on your thread's tag), if you cannot confidently determine which profile contains the current Outlook data, please contact your organization’s IT administrator before making profile-level changes. They can also help verify whether the historical IMAP messages remain available on the mail server or whether some of them exist only in the local Outlook profile.
Once the correct profile has been established, you can continue with the Spotlight reindexing guidance in A’s answer using that profile. Microsoft specifically requires the appropriate profile path when running the documented reindexing command.
I hope this information helps.