I have condition in my clients where all outgoing email from their server do relay into Relay server. This caused usually Public IP got blacklisted by RBL. I am perform the relay configuration by use this guidance : https://imanudin.net/2014/09/18/how-to-configure-outgoing-smtp-authentication-on-zimbra-8-5/
All email to outside well fine until found problem when sending email to some clients and getting error “too many hops”. Finally i am perform bypass for sending emails to some domains
– Perform configuration relay based on user/domain receiver like described in this link : https://imanudin.net/2014/12/25/relay-tips-based-on-userdomain-receiver-on-zimbra-8-5-8-6/
– But fill configuration file on /opt/zimbra/postfix/conf/transportfile so that like below
Note : destination-domain.tld is destination domain who cannot sent email by relay caused too many hops
Above configuration will bypass sending email to outside and not using relay server for outgoing.
Good luck and hopefully useful 😀