I'm using Thunderbird 128.3.3esr(g4 bit) on Windows 10. Sometimes (not always) an email arrives and I read it, but when I go back to look for it later, it isn't in the inbox, whether regular view or unified view. It still exists on the server (Gmail) and I can find it in search. This doesn't happen for every email, but it has happened more than once. There are no inbox filters that I know of. I've rebuilt the folder, same result. I've looked through similar reports online but not found anything that helps. Though I doubt it's relevant, I'll add that initially, unified view was empty, so I renamed the "smart mailboxes" folder as suggested online, and then unified view showed correctly. Suggestions?