Strange INBOX-Mirror

Hi -

I am looking at a strange phenomenon I can`t resolve: 

	One of our users has a mailbox that mirrors the INBOX. 

Incoming mails are displayed in both INBOX and „Name-of-Mailbox“. It is not any sort of „intelligent mailbox“ or similar. There is no rule pointing to that mailbox.
You can not rename or delete that mailbox, even if it`s empty. Neither in any mail-app nor in the webmailer-interface. 

There is no sub-folder for „Name-of-Mailbox“ (.mdir) on the server / within the User.macnt.

Does anyone have an idea of where to look?

Thanks
T I L L
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