Hello phoenix,
Sorry about that by this is my first post here :$
Also I've manage different ZCS and all with different version :'(
But I've update only the one related to this problem.
So regarding the problem, i did this to a specific user:
zmprov ma user zimbraMailTransport smtp

utgoing.dc.example.com:25
But my zmprov gs mailbox1.example.com | grep -i smtp
zimbraSmtpHostname: mta1.dc.example.com
zimbraSmtpPort: 25
zimbraSmtpSendPartial: FALSE
zimbraSmtpTimeout: 60
Take a note that outgoing isn't a zimbra server, so to speak, it's a simple postfix, which accepts to be my relay.
mta1 is a zimbra server which mainly purpose is to receive and send e-mail, and spam/virus processing.
My purpose is to have some specific users to to be relayed through a separated server. I thought that was the purpose of zimbraMailTransport in the account definitions? But I don't know which takes precendence.
Also I do those commands on the mailbox server (I have a multiserver deployment).
Thanks for all the help.