Mail: Since Tahoe, "all sent" doesn't show me all sent mail, just a few

I just upgraded to Tahoe a few days ago. I just realized that the "all sent" folder no longer shows me all the emails I sent recently. It looks like al the old sent emails ported over fine (though I can't easily verify this), but the new emails I send sometimes appear under "all sent" and sometimes not. Even if I do a search "To" a specific person, only some of the emails that I sent in the past few days show up.

I have multiple email accounts; each one has a shortcut under "all sent". If I select each account on its own, I see very few emails from the past 3 days; but in that case a search seems to work. For example, if I click on my business account, I see only 3 sent emails from the past 3 days. But if I search for emails sent to a specific person, I see 5 emails just to that person; and I know for a fact I emailed a lot more people.

This is a problem because I frequently need to refer to past emails, and when I do a search on a particular person or subject I want to see emails sent as well as emails received.

I made sure I have the latest update; and I restarted my computer a couple of times to see if it could make any difference, but no. What else can I try?