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If you wish to change the settings without performing a full ZCS restart then you can do :-
Code:
su - zimbra
postconf -e masquerade_domains="example.domain.com domain.com"
zmmtactl reload
this will not be persistent across restarts so for that you will need
Code:
su - zimbra
zmlocalconfig -e postfix_masquerade_domains="example.domain.com domain.com"