Mac Mail doesn't search

Mac mail does not search email.

I have several large mailboxes on Gmail and MS Exchange, and if I click in the search box or hit Option-Command-F I can enter text, like the name of a known contact "charlie" and hit return, and nothing happens. No filtering or finding happens, whether I've selected "All Inboxes", one of the Exchange mail inboxes, the Gmail inbox, or an old Unix imap mailbox.

I've cycled power, closed and restarted mail, cycled Apple/SystemSettings/Siri&Spotling/Mail&Messages (with and without closts and poweroffs) Mail/Mailbox/Rebuild on individual mailboxes and All Inboxes, taken the accounts off line, on-line, sychronized. Removed the mailboxes, re-added the mailboxes, mdutil -ia off and mdutil -ia on, all with reboots and restarts and nothing seems to fix it.

The search box happily holds my search term and does nothing at all to the the long chronological lists of emails.