I have foreign folders in my inbox and outbox

Default folders in Outlook (such as Inbox, Outbox, Sent Items, Drafts, Deleted Items, Junk Email, etc.) cannot be deleted or renamed. Outlook requires these folders to exist and will recreate them automatically if they are removed by other tools.

Only folders that were created manually can be deleted. To delete a user-created folder in Outlook for Windows, right-click the folder in the Folder Pane and select Delete Folder. Confirm to move it to Deleted Items. Note that built-in folders cannot be deleted this way and will remain.

If the “foreign” folders are duplicates of standard folders in an Exchange mailbox, they may have been created by sync or server issues. In that case, the supported approach is to:

1. Use a tool such as MFCMAPI to move any items out of the duplicate folder and then hard-delete the duplicate folder.
2. Start Outlook with the /resetfolders switch to rebuild the default folder set.

This process removes duplicate folders while preserving the required default ones.

References:

• # Can't delete default Outlook folders
• Delete a folder
• Remove duplicate folders in Outlook when connected to an Exchange Server mailbox