Mail is disappearing in Mozilla Thunderbirds inbox

Follow these steps if some or all of your messages suddenly disappear in Mozilla Thunderbird 45.7.0

1. Right click on the folder where messages are disappearing and select Properties

   

2. Click on the Repair Folder and then on OK

   

3. All hidden mails should be visible again. If the mails are still not showing, troubleshoot the problem using the steps listed here.