RBL is short for Realtime Blackhole List, a list of IP addresses whose owners refuse to stop the proliferation of spam. The RBL usually lists server IP addresses from ISPs whose customers are responsible for the spam and from ISPs whose servers are hijacked for spam relay.

Tech Logic Solutions uses these dynamic blacklists:

dnsbl.njabl.org
bl.spamcop.net
sbl.spamhaus.org
list.dsbl.org
cbl.abuseat.org
relays.ordb.org