outlook.com junk mail folder in iOS Mail not recognised

I have an outlook.com email address, which I access by web browser and Mail app on iOS.

The "Junk Email" folder is used by outlook.com as the designated junk folder, but iOS Mail does not recognise it as a Junk folder, thus the 'delete all' option is not available in iOS Mail. The iOS Mail app only seems to recognise the "Junk" (note spelling) folder.

The "Junk Email" folder appears in iOS in the folder tree in alphabetical order. It can't be renamed.

Note a solution I've seen proposed elsewhere is to add the account in iOS as "other" instead of using outlook.com presets - good idea, but unfortunately this has the side effect of disabling Push notifications! I've also seen seen other "solutions" including S/MIME... that's nonsense.

Has anyone found a fix for this? Is there a way to force iOS mail to recognise the "Junk Email" folder as the designated "Junk" folder?

Thanks

Bob