[Exim] condition for spam-scanning.

I have changed the condition used in the spamcheck_router in exim4.10
from

condition = "${if and { {!def:h_X-Spam-Flag:} {!eq
{$received_protocol}{spam-scanned}} {!eq {$received_protocol}{local}}
} {1}{0}}"

to

condition = "${if and { {!def:h_X-Spam-Flag:} {!eq
{$received_protocol}{spam-scanned}} {!eq
{$sender_address_domain}{sun.ac.za}}} {1}{0}}"

because the {!eq {$received_protocol}{local}} did not ensure that
emails originating from our domain are skipped.

But now I find that some emails that come from outside are not
scanned. How can I improve my condition?

Regards
Johann
--
Johann Spies          Telefoon: 021-808 4036
Informasietegnologie, Universiteit van Stellenbosch

     "Come now, and let us reason together, saith the LORD;
      though your sins be as scarlet, they shall be as white
      as snow; though they be red like crimson, they shall
      be as wool."                     Isaiah 1:18