[Exim] System Filters

I'm adding some clauses to a system filter, but I'd rather not receive
the message
back to postmaster@ in some cases.

e.g.

if
$h_subject contains "Here you have, ;o)" and not error_message and
$message_body contains "AnnaKournikova.jpg.vbs"
then
fail text "You appear to have been infected by the Onthefly/Anna
Kournikova worm (see http://www.f-secure.com/v-descs/onthefly.shtml)"
end if

As you can imagine, I probably don't want to know about every
virus-infected
sender in the world! Is there any way to prevent "fail" from sending an
email to
postmaster@ ? I couldn't find anything that looked promising in the
filter documentation
nor in the system filter part of the spec. It's certainly possible that
I overlooked
something though, in which case a point in the right direction would be
gratefully
received!

I don't simply want to prevent all postmaster@ mail from system filters
from being
delivered. On some occasions, the filter will alert me to something I
_ought_ to know
about!

Thanks,

Ollie