Mail search is useless for all but the simplest searches
This is obvious. Just try any search across all inboxes. The number of hits is small compared to the number of messages that match your search criteria. Hypothesis: the root cause of this issue is that the latest and greatest Mail releases on macOS (Ventura), iOS (16.2), and iPadOS (16.2) refuse to download messages from iCloud and Exchange servers. You can see the recipients, sender, and subject lines, but cannot EVER see the bodies of most messages. In my case only the most recent items in trash are EVER visible.
