Bounce management

Hi all

I have a problem with the bounce management. If I set a Custom return path (bounce) address in the Email settings, the Bounced Emails are sent there. But if I configure an address in the Monitored Inbox Settings, I don’t get anymore bounce mails.
The headers of the Emails look like this if a monitored inbox is configured:
Return-Path: <>, while is my Email which I configured as monitored. I’m suggesting the Return-Path address ist configured with VERP, but so the emails never come the How can I fix this?