[Exim] newbie+exim+mailscanner+cron=howto?

Hi!
I'm using Exim 4.20 with the "usual" Mailscanner setup, I mean one daemon only
queues (it has only a defer_router), Mailscanner filters and then transfers
the messages to the output queue, and another daemon does the real mail post
job from the output queue. Everything works fine with this setup, except one
thing: for eg. automatic locally generated cron mails won't get through...
Let me demonstrate it:

1A6F3t-0006EX-75 <= root@??? U=root P=local S=592 T="Cron <root@mystic>
run-parts /etc/cron.hourly" from <root@???> for root@???
1A6F3t-0006EX-75 == root@??? R=defer_router defer (-1): All deliveries
are deferred
1A6F3t-0006EX-75 ** root@???: retry timeout exceeded
1A6F3t-0006Ea-7k <= <> R=1A6F3t-0006EX-75 U=mail P=local S=1333 T="Mail
delivery failed: returning message to sender" from <> for root@???
1A6F3t-0006Ea-7k == root@??? R=defer_router defer (-1): All deliveries
are deferred
1A6F3t-0006Ea-7k ** root@???: retry timeout exceeded
1A6F3t-0006Ea-7k root@???: error ignored
1A6F3t-0006Ea-7k Completed
1A6F3t-0006EX-75 Completed

The pure configuration for the input handling daemon looks like this:
...
defer_router:
driver = redirect
allow_defer
data = :defer: All deliveries are deferred
varify = false
...

What could be wrong, any idea howto solve this problem?
Many thanks!
--
Jáger Sándor
science@???