TemasekTech is using a lists or RBL show below and Open Relay Database to block spam at the RBL level. We found that they provide a good first layer protection against spamming while minimizing any false positives. Our other layers of Spam Protection filters out the rest of the spams as much as we could.
Below is the lists.
b.barracudacentral.org
bl.spamcop.net
dnsbl.sorbs.net
sbl.spamhaus.org
spam.dnsbl.sorbs.net
rbl-plus.mail-abuse.org
cdl.anti-spam.org.cn
xbl.spamhaus.org
pbl.spamhaus.org
bl.spamcannibal.org