''re : We have several email accounts and every single device has an access to all of the accounts. '' Are they set up as imap accounts ? If yes, then emails are stored on server and the imap account provides a view of the emails stored on server. So first you need to know whether the emails exist. Logon to the webmail account. Are emails on server? In Thunderbird Check you do not have a filter effecting view. Select folder that has missing emails. Make sure the Quick Filter Bar is enabled. Are any of the icons on the Quick Filter Bar enabled /highlighted ? If yes, click on the icon to uncheck that filter. Note: some people forget to check the 'pin' icon. Make sure you have the full view of everything: View > Folders > select 'All' View > Threads > select 'All' Check to see if those missing emails have been set up as an ignored thread. View > Threads > select 'Ignored Threads' This may have accidentally selected by clicking email and then pressing on the shortcut key - K Read more info: https://support.mozilla.org/en-US/kb/ignore-threads