[Exim] Hidden delivery and exim -bp

After setting up some more or less unusual configuration, I noticed
the following:

When a global filter produces an outgoing message via unseen deliver,
this message doesn't show up when using sendmail -bp (or exim -bp)

The original message shows up with status 'D', but you can't see, why
its still in the queue.

Is this a bug or a feature I missed in the documentation?

-- 
Jochen Erwied <Jochen.Erwied@???>   Phone: +49-2151-7294-24
mbs GmbH, Roemerstr. 15, 47809 Krefeld          FAX:   +49-2151-7294-50