[Exim] Trying to block spam domain

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I'm running SA+Exim4.22+Exiscan

I am trying to block spammers from a certain domain.
I want to implement the following but I'm not sure
      ${lookup{$local_part}lsearch{/etc/mail/blacklist}}
/etc/mail/blacklist
*forbesdigital.com
*funcity.com

1) How would I create the ACL for this
2) How do I get exim to check that the host that is sending the mail has a
MX record.

Thanks
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