When you post a question it is helpful to include information so other Thunderbird users who offer help can understand your setup and type of account. At this moment all I know is "I updated thunderbird last night and now 20 years of emails are gone ". It's useful to know about any error messages or what you have tried. Therefore could you answer some questions... '''Q1:''' What Operating System are you using eg: Windows 10, MAC ? '''Q2:''' What Anti-Virus are you using? '''Q3:''' What Thunderbird version were you using prior to update? '''Q4:''' What Thunderbird version are you using now it has updated? '''Q5:''' Did Thunderbird start up and ask you to create a new mail account as if completely new? '''Q6:''' Did Thunderbird start up as normal and show you all the accounts and all the folders ? '''Q7:''' What type of account lost the emails....Are you talking about a POP account or an IMAP account or emails you store in 'Local Folders' mail account? '''Q8:''' You say emails are missing, but are the folders missing as well or are the folders still there but look empty? '''Q9:''' Did you lose all your emails in all your folders or only lost all emails in particular folder? '''Q10:''' If this is an imap mail account and some folders are missing, did you try to 'subscribe' to see those missing folders? '''Q11:''' If imap account, log on to your webmail account via a browser and find out if emails are still on server - what did you discover? '''Q12:''' Confirm you have these settings: * Menu app icon > 'View' > 'Folders' > 'All' * Menu app icon > 'View' > 'Threads' > 'All' '''Q13:'''As these emails are important to you, do you have a backup of your profile?