Setup:Thunderbird 52.1.1 (portable app); several imap accounts + my main mail working area in *local folders*. In my view I have the folder tree (including multiple imap mail boxes on top with their respective sub folders working fine) on the left pane. For my inbox and imap folders and normally also for my local folders I see a list of messages in the right-top pane and then the selected message in right-bottom pane. However, now my problem: in my email collection of ca. 40 GB in local folders when I navigate to seldom used, old folders (=click the folder in the left folder tree pane), instead of showing the messages in this folder in the right-top pane I only get "Thunderbird Mail - [folder name]" (see example image attached). o I get to see the messages when I press F2 + enter (to rename the folder but merely accept the existing name) and then click the folder again; now the contained messages appear in the list o I have tried to delete all index files and recreated them; this takes several hours with my local folders size but does not cause any change in the described behavior This problem has persisted for few years now; I continue using Thunderbird for some 15+ years now and it would be painful to have to change the e-mail client software, but this is getting troublesome. Anybody any help? Over the last couple of years I have tried to google and search also the support.mozilla for similar experience and solution but no luck.