[Exim] queuerunner

We run mailing lists on behalf of our clients.
If there is a new announcement which they want to mail to their
subscribers (! note this is *not* spam ;) )
I often have to relay >10,000 messages. Exim starts to queue at some
point (I can hardly send out 10000 emails rightaway ;) )
However, the queuerunner seems to process only one message after the
other. That isn`t really satisfying, because
a dns lookup might take a few seconds and is blocking.
I rather see exim fork of say 100 processes and process the queue with
all of them.
I tried remote_max_parallel (which appears to only work during the
initial submission to exim)
and queue_run_max is also set to 100.
why do I get exim to deliver these more efficently?

Thanks in Advance,
Conrad Wood