Вернее можно так
deny message = rejected because $sender_host_address is in a black list at $dnslist_domain\n$dnslist_text
dnslists = ${readfile { /etc/mail/dnsblists }{:}}
#cat /etc/mail/dnsblists
cbl.abuseat.org
zen.spamhaus.org
bl.spamcop.net
dnsbl.sorbs.net
http.dnsbl.sorbs.net
socks.dnsbl.sorbs.net
misc.dnsbl.sorbs.net
smtp.dnsbl.sorbs.net
web.dnsbl.sorbs.net
spam.dnsbl.sorbs.net
dul.dnsbl.sorbs.net
combined.njabl.org
dnsbl.njabl.org
dnsbl.ahbl.org
list.dnswl.org
cbl.anti-spam.org.cn
relays.mail-abuse.org
spam.abuse.ch