[exim] protected addresses ACL

Hiya,

I'm trying to create a "protected addresses" ACL to protect mailing lists such
that certain email addresses can only be sent to from certain IP addresses,
possibly by using some sort of lsearch:

address1@???: 10.2.1.5 : 127.0.0.1 : 14.23.19.1
address2@???: 192.168.0.1 : 14.23.19.1
address@???: 11.4.3.219

I was thinking along these lines, but I'm not quite sure how to finish it off:

acl_smtp_rcpt:
  # blah blah
  accept local_part = lsearch;/path/protected-addresses
         endpass
         verify = recipient
         hosts = ${lookup{$address}lsearch{/path/protected-addresses}

Any suggestions?

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