Big problem we can't send mails from Thunderbird via our Zimbra SMTP server, I have to add the from public IPs addresses in main.cf in $mynetwork but each time I restart Postfix I loose the config.

Two questions :

1 - Does Zimbra work as IMAP_BEFORE_SMTP feature to open the SMTP relay ?

2 - How to set $mynetwork to keep his configuration in each restart ?