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

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 reject comment below


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