Zimbra 8.6 restrict to user sending mail to certain domain

How to restrict to user sending mail to certain domain. To configure on zimbra mta.

Step 1: To add lines in file /opt/zimbra/conf/zmconfigd/smtpd_sender_restrictions.cf as bellow:

#vi /opt/zimbra/conf/zmconfigd/smtpd_sender_restrictions.cf

Adding lines the top as following:

check_sender_access lmdb:/opt/zimbra/postfix/conf/restricted_senders

Step 2: To add lines in file /opt/zimbra/conf/zmconfigd.cf

vim /opt/zimbra/conf/zmconfigd.cf

Adding the lines following before RESTART mta.

POSTCONF smtpd_restriction_classes local_only
    POSTCONF local_only FILE postfix_check_recipient_access.cf
    RESTART mta

Step 3: To create file "/opt/zimbra/conf/postfix_check_recipient_access.cf"

vi /opt/zimbra/conf/postfix_check_recipient_access.cf

Adding the lines following:

check_recipient_access lmdb:/opt/zimbra/postfix/conf/local_domains, reject

Step 4: To create file "/opt/zimbra/postfix/conf/restricted_senders" and list all user whom you restrict.

vi /opt/zimbra/postfix/conf/restricted_senders

Adding the lines following:

[email protected]            local_only

If you restricting all users in domain.

yourdomain.com            local_only

Step 5: To create file “/opt/zimbra/postfix/conf/local_domains” to list all domain where restrict to user sending mail.

vi /opt/zimbra/postfix/conf/local_domains

Adding the lines following:

yourdomain.com                     OK
otheralloweddomain.com      OK

Step 6: Run command the below to apply.

postmap /opt/zimbra/postfix/conf/restricted_senders
postmap /opt/zimbra/postfix/conf/local_domains
zmmtactl stop
zmmtactl start

*Note: I’m not survive when you upgrade system. Before upgrade you backup the configrue
If you undo this configure.

#postconf -e smtpd_restriction_classes=' '
#zmmtactl reload

Source: https://wiki.zimbra.com/wiki/Restrict_users_to_certain_domain