Trash folder not synced by IMAP

Support
1

It seems like when I move an item to ‘Trash’, it is stored in some local Trash folder, rather than being synced to my IMAP ‘Trash’ folder.
Conversely, when I move an item to ‘Trash’ in one of my other IMAP MUA apps (e.g., EMACS mail, Outlook), it fails to sync and show up in the K9 ‘Trash’ folder.

Is there any way to ensure that the K9 Trash folder gets treated as an IMAP folder rather than as a local trash folder?

2

Check Settings / account / Folders
Here the mapping between local and remote folder is done.

3

I think I solved it by setting the ‘Trash’ folder to ‘Automatic (Trash)’ rather than the option I had set before ‘Trash’ – not really sure what the difference is or should be between the two.