thanks for the fast answer - I was not aware of the difference between
the user and the kernel limit, after using the limits.conf inside the
guest it is doing fine.
The missing entry in context was just looking at the wrong context - if
one is in hurry (which you will be if your mailserver runs out of
handles) some things are not that smooth as they should be...
-- Protect your environment - close windows and adopt a penguin!