Preventing backscatter on aliased domains in Zimbra

By default, an aliased domain in Zimbra will accept all e-mail at SMTP time and then bounce a message later if it is unable to delivering it after carrying out the aliasing. This generates backscatter, which can be abused and even lead to your mail server appearing on some blacklists. Luckily, since Zimbra 5.0.12 there has been a way to fix this; just su to the zimbra user and run:

zmlocalconfig -e postfix_enable_smtpd_policyd=yes
zmprov mcf +zimbraMtaRestriction “check_policy_service unix:private/policy”
postfix stop
postfix start