How to find the host name host `hostname` Domain level blocking of users

ZCS8: zmlocalconfig -e postfix_smtpd_sender_restrictions=”hash:/opt/zimbra/postfix/conf/reject”

ZCS8: Add hash:/opt/zimbra/postfix/conf/reject as the first line of /opt/zimbra/conf/zmconfigd/smtpd_sender_restrictions.cf

user@domain.com REJECT domainX.com REJECT

Restart zimbra postmap /opt/zimbra/postfix/conf/reject zmmtactl stop && zmmtactl start