Are you sure you deleted them? Perhaps you have chosen a view that does not include all your folders. Check: View > Folders > set to 'All'

Check the 'Trash' which will show a > on left side of 'Trash' folder indicating it has some deleted folders.

Note: if you have set 'Account Settings' > 'Server Settings' for the account to Empty the Trash when you exit Thunderbird then this may explain why they not in the 'Trash'.

If this is an imap account: Logon to webmail account via a browser to see if those folders still exist on server. If they do not exist on server then you cannot subscribe to see something that does not exist. If they exist on server, then try to 'Subscribe' to see them. right click on imap mail account name folder in Folder Pane and select 'Subscribe' select folder and click on 'Subscribe' click on OK

If View > Folders is set to All and nothing in Trash nor on server as viewed via webmail, then do you have a backup of your profile folders ?

Todd-Hall I did all what you recommend but I don't see them anywhere. View is set to all and I logued in in webmail and there are not there either. Any other recommendations you might have ?

Thank you

I'm assuming you are using IMAP . If they are not on the server (viewed via webmail) then you not be able to see them because they do not exist. You need to understand that imap accounts offer a view of the server; they can only display what is on the server. Imap accounts cannot be considered a separate independent copy because emails are stored on server and imap folders synchronise to show what is on server. In effect, the folders in an imap account are one and the same as folders on the server.

Anything you do in Thunderbird imap account is also done on server. Anything done directly via webmail will also be reflected in Thunderbird imap account.

Check to see what is currently in the profile folders. Help > Troubleshooting Information Under 'Application Basics' about 8th down in list is 'Profile Folders' - click on 'Open Folder' button

A new window opens showing contents of Profile name folder. Click on 'ImapMail' folder click on imap mail account name folder

Folders you normally see in the Folder Pane will appear as files with same name. If you downloaded full copies then you would see mbox text files. They have same name as folder, but do not have an extension. They contain full copies of emails. Any file with a .msf extension is just an indexing file. If you only see *.msf files and no same name mbox files then you have only downloaded headers. If you see any folder with *.sbd extension then this means you have created subfolders and these folders may also contain mbox/.msf files and possibly *.sbd folders if they had sub folders.

Can you see any files/folders even in the *.sbd folders with the same name as the 'deleted' folders? If yes, then I need you make sure you have 'View set to show details. Make window big enough to show as many files etc as possible. Then create and post images so I can see every file and folder that is in your imap account. Tell me the names of the folders that are 'deleted'/missing. I will then check through your images to see whether the folders exist, but are not visible due to a missing mbox file.