Using mbox format and this namespace
namespace { inbox = yes hidden = yes prefix = INBOX/ }
[Though I've also tried, seemingly, a million different namespace options to "fix" my problem.] It's a migrated setup from a 1.x dovecot install from Ubuntu 12.04, now on 16.04
The problem is in TBird [I haven't tested with any other mail clients] and IMAP; with that name-space I get all the folders both at the root level [same as inbox], as well as below inbox. [The same folders, pointing at the same underlying messages.]
For example, if there's a folder "blah" and I subscribe to it, "blah" shows both at the same level as inbox, as well as a sub-item of inbox. If I unsubscribe from folder "blah" it also unsubscribes from the subfolder "blah" under inbox, and at the root level. [I hope that's clear enough...]
This is not a terrible problem, but it's cosmetically ugly and confusing for users. I'd prefer to only see these folders as subscribed as sub-folders [or sub-items] under inbox.
I'd guess I'm making some stupid beginner error, but I've not been able to figure it out, as of yet. Any help would be greatly appreciated.
-Greg