I need to do a "weird" thing: for some (or eventually all) local recipients, I need to deliver using an external MTA.
So, say my server handles @example.com, and I use relay.myisp.com as external MTA, I need that ALL mails go thru relay.myisp.com, even if I'm sending to firstname.lastname@example.org which is handled locally by zimbra.
Mails will then get back (via fetchmail), and delivered as usual.
So, the rule would be: mails generated locally for local accounts, gets outside anyway.
How do I accomplish this?