unknown smtpd restriction: "reject_unknown_reverse_client_hostname"

Error is in postfix configuration. If I enable the above in order to try and keep a BUNCH of the spam down, I keep getting this error in the mail.log file on almost all smtpd entries. Please help.

Also, I sent several other emails to Joe over the weekend. Waiting for a response to those.. Just a heads up that they are there.

Status: 
Closed (fixed)