This bug was reported 28 days ago and has yet to be resolved. https://bugzilla.mozilla.org/show_bug.cgi?id=1857734 The temporary fix for the unpopulated unified folders including the Sent folder, and the issues with missing messages, some showing up in individual folders and not the unified folder and vice versa were just that, temporary fixes. Yesterday, the Sent folder was back to being unpopulated, and the individual folders containing my important and starred messages were all open for some mysterious reason. How this happened out of the blue is also a mystery, because I was not notified of an upgrade. If upgrades are installing on my computer without my permission, this is completely unacceptable. This is a subject that needs to be taken seriously at this point.