You can use any of the below in the MTA SMTP Options (inbound) settings under Realtime (SBL) Blacklists:
bl.spamcop.net - Default in InterWorx.
zen.spamhaus.org
bl.spamcop.net
b.barracudacentral.org
dnsbl.sorbs.net
cbl.abuseat.org
You can use any of the below in the MTA SMTP Options (inbound) settings under Realtime (SBL) Blacklists:
bl.spamcop.net - Default in InterWorx.
zen.spamhaus.org
bl.spamcop.net
b.barracudacentral.org
dnsbl.sorbs.net
cbl.abuseat.org