smtp processing local with forwarding

[jocx]

hi.
I'd like all email on my zimbra server to get forwarded to
an external smtp host for relay processing.
In Ajcody-MTA-Postfix-Topics - Zimbra :: Wiki
there is mention of setting zimbraSmtpHostname for global and server
settings, but that doesn't forward local client smtp submitted messages.
Another down side is that webclient submission has some delay as
the external smtp hosts may be slow in processing.
What I'd prefer is that the local smtp zimbra engine accept
handoffs from zimbra webclient or other clients based on
the zimbra server, and then forward the messages to the
external smtp engine.
Ajcody-MTA-Postfix-Topics - Zimbra :: Wiki
mentions
Postfix After-Queue Content Filter
I wonder if anyone has tried this and if it seems like a good solution for
forwarding all messages to off-zimbra for processing.
also please see https://bugzilla.zimbra.com/show_bug.cgi?id=41603
thanks,
John