Zimbra Error 450 4.7.1 sender reject
In this tutorial, How to solve problem "zimbra Error 450 4.7.1 sender reject" on Zimbra MTA. Zimbra Error 450 4.7.1 sender reject as below Feb 10 16:16:33 sd-15xxx postfix/smtpd[1832]: NOQUEUE: reject: RCPT from unknown[x.x.x.x]: 450 4.7.1 Client host rejected: cannot find your hostname, [x.x.x.x]; from=<[email protected]> to=<[email protected]> proto=ESMTP helo=<smtp_sender.com> You can check step by step to solve problem as error above Step 1: Check smtpd_sender_restrictions on zimbra MTA. [zimbra@your_mta ~]$ postconf | grep "smtpd_sender_restrictions" Checking reject_unknown_sender_domain,reject_unknown_client_hostname,reject_invalid_helo_hostname is correct your environment Step 2: Check server port 10031 on zimbra cbpolicy. tailf /opt/zimbra/log/cbpolicy.log To check the database have lock? sometime due to cbpolicy. You can solve problem anything else? share your error Zimbra Error 450 4.7.1 sender rej