I finally relented and upgraded Mozilla Thunderbird to 24.0.1. The only change I notice is that now all my incoming mail goes to the Trash folder. This is approximately correct, but there is occasionally something I'd like to read. Looking online I see stuff about filters. The only filter I have on Inbox is "Chinese spam" which looks for "helo" in Received-SPF (I can't recall when or why I created that). Has anyone else seen this problem?