I've used Thunderbird on Windows for years and have hundreds of messages saved in local folders. I "guard" 4 different accounts, 2 at gmail and 2 at my local service provider. For several months now, when I launch Thunderbird I see it checking the 4 mailboxes and I see the correct number of new messages in parens after the mailbox name in the Inbox tab. But some of those new messages do not appear in the Inbox list. If I then click on each of the 4 mailbox names under the Inbox tab, the new messages do appear. Or, if I close and immediately relaunch Thunderbird, all new messages appear, no problem. I've updated Thunderbird and Windows, yet the problem continues. I suspect a corruption in the TB database, but I don't see any options to clean, compress, fix the database.