Preventing clients from trying to create folders under inbox

[Bryan K. Walton]

Our Dovecot installation is configured as such:

mail_location = mbox:/var/vmail/%u:DIRNAME=.mboxdata:INBOX=/var/vmail/%u/INBOX:INDEX=/var/vmail/indexes/%u

This allows us to continue using mbox formatted files, storing those
mbox data files in a file called .mboxdata.  This allows our users to
create folders and subfolders.  The only exception to this is our
inboxes, which are more traditional mbox files.

However, we have some Outlook users that insist on trying to create
subfolders of their inbox.  This doesn't work, since the inbox is a
file.  But Outlook still does it and it causes sync issues, as there is
now a subfolder under the user's inbox, but that subfolder is ONLY
present in Outlook (it isn't present on the server).

Is there anything that we can configure so that Dovecot instructs
Outlook that it cannot attempt to create subfolders under the inbox, but
allow subfolders elsewhere?

Thanks!
Bryan