Postfix
Here is a sample of one user's main.cf where the SCBL is used:
- smtpd_recipient_restrictions =
 - reject_invalid_hostname, 
- reject_non_fqdn_sender,
 - reject_non_fqdn_recipient,
 - reject_unknown_sender_domain,
 - reject_unknown_recipient_domain,
 - reject_unauth_pipelining,
 - permit_mynetworks,
 - reject_unauth_destination,
 - reject_rbl_client bl.spamcop.net
 - permit
  - reject_non_fqdn_sender,
 
Another example using several BL's is available at http://jimsun.linxnet.com/misc/postfix-anti-UCE.txt
[Append to This Answer]