[Exim] Spoofing

Is there a way to detect and reject spoofed email via the filters or something?

In other words, emails spoofed as being from address@??? but coming
from a machine outside our company.

Could it be with something like:

if $header_from contains "@ourdomain.com" and
   $header_message-id does not contain "@*ourdomain.com"
then
    seen finish

Or some other method?

I searched for spoof in the email archives at www.exim.org but did not get my search
target.

Thanks,

Guru