SAEximRunCond help please

I want to add a condition to my SA-Exim that tell is ONLY to scan email for
my domain(s).

I would prefer to have a text file with the valid domains I host email for.

My problem now is that I am a backup MX for several domains, and every
single email coming through me is scanned (and some messages dropped becuase
they are spam.   Some of the domains  I backup for have their own
white-lists, black-lists, and special requirements that are being affected
by my spamassassin settings here.  I am actually deleting emails that might
be on their white list.  (this is very bad).



How can I do this.  I read the archives, and noted some trying and failling
when using the $domain variable.


I do NOT write much regex code.  Any help will be greatly appreciated.

Thank You

Terry Shows
Computer Software Specialists LLC
[email protected] <mailto:[email protected]>