Check current setting.
$ zmprov gacf | grep zimbraMtaRestriction
Output:
zimbraMtaRestriction: reject_non_fqdn_sender
Currently reject_non_fqdn_sender is set.
Adding sbl.spamhaus.org
$ zmprov mcf zimbraMtaRestriction reject_non_fqdn_sender zimbraMtaRestriction "reject_rbl_client sbl.spamhaus.org"
Check the result:
$ zmprov gacf | grep zimbraMtaRestriction
zimbraMtaRestriction: reject_non_fqdn_sender
zimbraMtaRestriction: reject_rbl_client sbl.spamhaus.org
Other options
zmprov mcf
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 dnsbl.sorbs.net"
zimbraMtaRestriction "reject_rbl_client sbl.spamhaus.org"
zimbraMtaRestriction "reject_rbl_client relays.mail-abuse.org"
According to zimbra wiki
