(I assume you are using only one POP account.)

By default, you can’t, as Local Folders is a special account.

However, you could try this:

• Remove the corresponding files (Trash.*, Junk.* and Sent.*) under the Mail/Local Folders folder in your profile folder (open Help > Troubleshooting Information and click Show folder to show/open the profile folder). Trash.* (as with Unsent Messages.* for Outbox) however will probably be recreated since these 2 are required - they will also appear when adding a POP account for the first time.

• Or install the Hide Local Folders add-on to hide Local Folders completely. I can’t tell what happens if you actually use some of the folders (like Archives and the one at the bottom), so you would just have to try, or set up Thunderbird to save these messages elsewhere.

Thanks for your reply. You're correct a deleted folder (junk, sent, trash) gets recreated - but only if a file is moved into the folder. The Junk folder and Icon can be permanently deleted by changing Account Settings/Local Folders/Junk Settings so junk messages are moved to the parent email account. Unfortunately, there's no similar setting accessible for the Sent, Trash or Archive folders. Perhaps I need a look at the source code and suggest and add-on.

Many of us actively use Local Folders so, to us, these folders are useful and valuable. Those folders would be used by default if you made use of Thunderbird as a news reader. They are there for a reason, and so it's not "a mistake" that they are there.

Open your profile, close Thunderbird, open Mail then Local Folders, delete all the folders you don't like. Thunderbird will put back the ones it thinks you should have or might need. You're looking for Inbox, Sent, Trash and so forth. Deleting other folders such as mozmsgs etc won't make any difference as they don't appear in the account pane. But if these folders do exist then it suggests you have unknowingly made use of Local Folders.