This is only peripherally related to Linux, since that's what I use. I have this weird, new, inexplicable issue with my mail client, SeaMonkey.
When I search within one specific
folder, it yields no results. And what's crazier is that if I move some of the messages from that folder to another folder and then search in their new location, I STILL get no results.
I'm doing what I've done for DECADES (SeaMonkey was formerly the Mozilla Suite, which was Netscape Communicator before that), but definitely not getting the expected results!
Searching any other folders or messages, using the exact same search criteria, i.e., searching within the body of the messages in a folder, works.
The e-mails in question are plain text.