:? que o postfix esta me tentando dizer com esse log e como posso solucionalo ?

Unrecognized warning:
14.2.168.192.bl.spamcop.net: RBL lookup error: Name service error for name=14.2.168.192.bl.spamcop.net type=A: Host not found, try again : 1 Time(s)
14.2.168.192.blackholes.mail-abuse.org: RBL lookup error: Name service error for name=14.2.168.192.blackholes.mail-abuse.org type=A: Host not found, try again : 1 Time(s)
14.2.168.192.dnsbl.njabl.org: RBL lookup error: Name service error for name=14.2.168.192.dnsbl.njabl.org type=A: Host not found, try again : 1 Time(s)
14.2.168.192.list.dsbl.org: RBL lookup error: Name service error for name=14.2.168.192.list.dsbl.org type=A: Host not found, try again : 1 Time(s)
14.2.168.192.opm.blitzed.org: RBL lookup error: Name service error for name=14.2.168.192.opm.blitzed.org type=A: Host not found, try again : 1 Time(s)
25.2.168.192.blackholes.mail-abuse.org: RBL lookup error: Name service error for name=25.2.168.192.blackholes.mail-abuse.org type=A: Host not found, try again : 1 Time(s)