[exim] Don't check mail from any local domain for spam if it…

Hi,

Is it possible to not check mail from domains in local_domains for spam
if the message contains the header X-Spam-Flag: and it comes from one of
the mx's for the domain? Something like:

if not (domain in local_domains
and host in mx for domain
and header x-spam-flag) do check spam

I guess I could figure it out if I knew if it is possible to check if
the host is in the mx for the domain...

Best regards,
Stian