I am trying to divert all local mail also via an external antispam/antivirus service. The Admin console setting won't do this. I don't want to enable antivirus, antispam service in zimbra and setup some rules there trying to fool the system. Simple plain, I want to be able to directly put value in /opt/zimbra/postfix/conf/main.cf. I can do this after I start Zimbra services via the postconf like this:

> postconf -e content_filter=smtp:[av.as.server]
> postfix reload

This works fine, I tested, but if I restart the Zimbra service, the value is reset to blank/null.

So without enabling Antivirus & Antispam services in Zimbra, then setting up filters etc how do I ensure the main.cf content_filter value is persistent across reboots/restarts?

Can someone help me out?