Keeping known email abusers out is always desired. Postfix has a parameter which is specified in the main.cf file that allows you to refer to these lists.
The script I use is as follows…

smtpd_client_restrictions =
	permit_mynetworks
	permit_sasl_authenticated
	reject_unauth_pipelining
	reject_rbl_client cbl.abuseat.org
	reject_rbl_client dnsbl.ahbl.org
	reject_rbl_client dnsbl.sorbs.net
	reject_rbl_client list.dsbl.org
	reject_rbl_client sbl-xbl.spamhaus.org
	#reject_rhsbl_client blackhole.securitysage.com
	reject_rhsbl_client rhsbl.sorbs.net
	permit

Note the commented out line

	#reject_rhsbl_client blackhole.securitysage.com

See below
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This is a list that was not properly administered. A friend of mine tried to email me who uses the mac.com domain and was being rejected as an abuser which, of course, is rediculous.
I keep the entry as a future reference. There are others out there so if you know of them please let me know.
mta.