What continues to puzzle me is why you still like to put (and/or leave) as Draft Emails (unsent) in your Outbox?
I also noticed you said "Outbox Folders" ... plural. I only have one real Outbox (the one that works with my main Folders.PST file). Over the years and Outlook versions, it's always been that way. If like I do ... you also use iCloud for Windows ... you might see another Outbox in the Apple iCloud virtual thing (but I never use or mess-with that section, I just let it to it's iCloud stuff).