[Exim] local_part and domain in data acl

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Im trying to get spamassassin to scan only selected emails based on a list
of email address's in a flat file. In my RCPT ACL I use:

         condition     =
${lookup{$local_part@$domain}lsearch{/usr/exim/spam}{true}{false}}

but from what ive read in the docs I cant use $local_part or $domain in the
DATA ACL which is where the spamassassin check takes place. I think I may
have to use some sort of expansion variable such as $acl_m0 but im not 100%
sure and my attempts to do so have failed.

Any pointers on what I need to do or what im doing wrong?
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