''re :our old folders and contents (emails) of two accounts from previous version were completely lost.'' I'm presuming you had 3 accounts and 2 are not displaying in the Folder Pane. Are your missing accounts IMAP or POP? Are they displaying in the Account Settings. In Account Settings Can you see a list of all the mail accounts? What is in that Account Settings? When Thunderbird started up did it act like a new set up ? Did it ask you to create a new mail account ? What do you see in this location: * In Thunderbird * Help > Troubleshooting Information * Under 'Application Basics' near the botton - Profiles - click on 'about:profiles' * It opens in a new tab. * Post an image showing all the contents in that 'about:profiles'. Then do this. * In computer search type : %Appdata% - see image below as guide. * Select %Appdata% file folder * click on 'Roaming' * Click on 'Thunderbird' folder. * locate 'profiles.ini' file and open it using 'Notepad', * Copy all contents and paste info into this forum question.