To actually use this software after package installation you need to configure postfix to use it Edit postfix configuration files: put somethink like the following into /etc/postfix/main.cf: smtpd_recipient_restrictions = reject_unlisted_recipient ... reject_unauth_destination check_policy_service 127.0.0.1:10001 For the size acl to work correctly, apolicy need to be called this way: smtpd_end_of_data_restrictions = check_policy_service 127.0.0.1:10001 edit the example acl /etc/apolicy/policy.conf to adapt to your environment. remember to enable and start the apolicy service: chkconfig apolicy on service apolicy start or postfix will fail.