dnsrbl

make sure the DNSRBL lists you are targeting are still alive. the test can be done according to the very specific RBL mechanism and using generic listing.

for zone in \
    bl.spamcop.net \
    public.sarbl.org \
    cbl.abuseat.org \
    psbl.surriel.com \
    db.wpbl.info \
    ix.dnsbl.manitu.net \
    b.barracudacentral.org \
    zen.spamhaus.org \
    ; do
    echo $zone
    host 2.0.0.127.$zone && echo OK || echo NOK
    echo
done; unset zone

those seem to be gone

dnsbl.inps.de
bl.blocklist.de

# closed effective 2012-10-30
bogusmx.rfc-ignorant.org
dsn.rfc-ignorant.org

some notes about too restrictive lists

# this sometimes blocks gmail...
#   reject_rbl_client dnsbl.dronebl.org,

# this blocks hh.ru
#        reject_rbl_client truncate.gbudb.net,

# this blocks nine.pairlist.net / hackrf-dev-bounces@greatscottgadgets.com
#       reject_rbl_client spam.spamrats.com,

# those block orange.fr...
#       reject_rbl_client dnsbl.sorbs.net,
#       reject_rbl_client dnsbl-1.uceprotect.net,

# The RFC-Ignorant.org DNS lists are closed effective 2012-10-30.
#       reject_rhsbl_sender bogusmx.rfc-ignorant.org,
#       reject_rhsbl_sender dsn.rfc-ignorant.org,

# this is too restrictive
#       reject_rhsbl_sender dsn.rfc-clueless.org,

# apews is blocking online.net ip range
#       reject_rbl_client l2.apews.org,