Version 52.9.1 automatic update, On 13th July.The disappearing act started. Emails downloaded that day stayed in Inbox. When shutting down computer and restarting Thunderbird all of a sudden only email from 2012 showed up only apparently folders for 2012,2013,2014 only now exist but only showing in inbox the year folder clicked only. so showed about 156 of 35,000 emails.No 2015,2016,2017,2018 folders. Going into sent emails ALL SENT EMAILS FROM 2012 to CURRENT DAY STILL EXIST, There are new emails downloaded from my provider show up but if , Thunderbird closed, computer restarted those emails for the day would vanish.All the emails still showed up on the providers web site, but would not replace the emails vanished from Thunderbird. Going into In box and searching for emails from know people the search would be fruitful giving all emails in the inbox from July 2018 to 2012. I did try downloading Thunderbird again, there was a big improvement now emails from mid 2015 to 2012 would show up in the inbox about 15953 against previously 156 about half emails. Also what improved when going out of thunderbird shutting the computer down and restarting I now did not have the newer email vanish as before. So ALL EMAILS DO EXIST IN THE INBOX JUST THEY ARE INVISIBLE AS WELL AS THE 2015,2016,2017,2018 Folders. I will see if I can download an earlier version and see what happens. Yes ALL THE EMAILS ARE THERE SOMEWHERE JUST IN AN INVISIBLE FORM. Note this is the only problem I have had since 2012 with ThunderBird. I have downloaded Version 52.9.1 again results staying the same, I have downloaded Version 52.2.0 results the same Reloaded version 52.9.1 Appears the same I will shut the computer down and restart incase a difference occur,