About a month ago we started receiving lots of spam emails so I followed the instructions here:
Configuring and Monitoring Postfix DNSBL - Zimbra :: Wiki
to have our mail server use DNS Blacklists to reject spam and added all possible RBLs, including dnsbl.sorbs.net.
Dnsblcount (setup as per the instructions listed on the above website) is showing that our server is rejecting around 1000 emails per day, and we are receiving markedly less spam.
The issue is that several customers of ours are receiving bounce emails that indicate that the sorbs.net blacklist is causing our mail server to reject their emails. These false positives seem to be isolated to the sorbs.net RBL, so I re-did our DNSBL configuration to include all possible RBLs except sorbs.net and restarted the mail server.
Here is the current output of "zmprov gacf | grep zimbraMtaRestriction"
This indicates to me that dnsbl.sorbs.net is no longer being used, however, we are still having sender's email rejected as a result of their being blacklisted on sorbs.net and dnsblcount is still showing sorbs.net as one of the rejectorsCode:zimbraMtaRestriction: reject_invalid_hostname zimbraMtaRestriction: reject_non_fqdn_hostname zimbraMtaRestriction: reject_non_fqdn_sender zimbraMtaRestriction: reject_rbl_client dnsbl.njabl.org zimbraMtaRestriction: reject_rbl_client cbl.abuseat.org zimbraMtaRestriction: reject_rbl_client bl.spamcop.net zimbraMtaRestriction: reject_rbl_client sbl.spamhaus.org zimbraMtaRestriction: reject_rbl_client relays.mail-abuse.org
Even though I removed sorbs.net from the MtaRestrictions list as of 06/02/11, today's (06/07/11) dnsblcount report shows:
We need our server to stop rejecting email based on the sorbs.net RBL. Any followup on this is greatly appreciated.cbl.abuseat.org 904
Total DNSBL rejections: 1536
As an aside, is it possible to have postfix do other things with these emails rather than reject them (mark as spam, for example)?