Domain level blocking of users
Below mentioned are the steps to "REJECT" an external email address from sending mail to the users of the Zimbra Domain.
The same results can also be achieved via link blacklisting.
1. Edit /opt/zimbra/conf/zmmta.cf
Add this line below (smtpd_recipient_restrictions) POSTCONF smtpd_sender_restrictions FILE postfix_sender_restrictions
2. vi /opt/zimbra/conf/postfix_sender_restrictions
3. Create file /opt/zimbra/postfix/conf/reject with the list of email address to be rejected in the below format:
4. postmap /opt/zimbra/postfix/conf/reject
5. zmmtactl stop ; zmmtactl start
Please note that this change will not survive an upgrade and you will have to redo these after the upgrade.