re :I used to have an inbox folder, under which I had all inbox folders from all my accounts. And this was done automatically, by thunderbird, I didn't created it.

I think you are talking about using a Unified folders view and you would have to enable it. The normal default is: View > Folders > 'All'

You are describing something which sounds like this is selected: View > Folders > Unified If you have Unified view selected and you do not want it then uncheck Unfied and select 'All'

re :But after the update, this inbox folder is empty. The only way to see mails is to go to the inbox folder within each account.

If the 'Unified Inbox' does not have a sublist of account Inboxes or some are missing do this:

• Right click on the Unified Inbox folder and select 'Properties'
• Click on 'Choose '
• For each account select the 'Inbox'
• click on 'OK
• Click on 'Update'

If it seems corrupted do this:

• View > Folders > select 'All'
• View > Folders > uncheck 'Unified'

• Help > Troubleshooting Information
• Under 'Application Basics' - half way - Profile Folders - click on 'Open Folder'

A new window opens showing the contents of your profile name folder

• Exit Thunderbird now.

• Scroll down and delete this file : 'virtualFolders.dat'
• Click on 'Mail' folder to see contents
• Delete this folder : 'smart mailboxes'

Start Thunderbird Allow time for accounts to check for mail etc.

If you want to see Unified folders do this:

• View > Folders > select 'Unified'
• View > Folders > uncheck 'All'

The part of deleting 'virtualFolders.dat' & 'smart mailboxes' fixed the problem.