Okay, here is mine
Code:
[zimbra@office ~]$ zmprov gacf | grep -i mtarestriction
zimbraMtaRestriction: reject_non_fqdn_sender
zimbraMtaRestriction: reject_invalid_hostname
zimbraMtaRestriction: reject_rbl_client b.barracudacentral.org
zimbraMtaRestriction: reject_rbl_client zen.spamhaus.org
zimbraMtaRestriction: reject_rbl_client dnsbl.sorbs.net
for the barracuda one you would need to sign up too
Barracuda Central and then to implement the RBLs use
Code:
su - zimbra
zmprov mcf +zimbraMtaRestriction "reject_rbl_client b.barracudacentral.org"
From your post you may have already read
Improving Anti-Spam system :: Wiki ? Also search the forums for BackScatter.