Zimbra restriction of forwarding to addresses within the domain

[GustavoFring]

I am trying to find a solution to my problem. We are deploying Zimbra in our company and I need to restrict users from forwarding messages only to addresses within our domain, so that no one can forward mail to private email accounts. What is the simplest way to do this in Zimbra version 10.1.10?

[Klug]

AFAIK there's no such feature in ZCS.

What I would do:
forbid the users to setup forwarding address (in the admin panel: CoS - Mail Feature - "Allow the user to specify a forwarding address").
make (domain) admins add a forwarding address when needed (using the admin panel: Account - Forwarding - "User-specified forwarding addresses").

[adrian.gibanel.btactic]

I am trying to find a solution to my problem. We are deploying Zimbra in our company and I need to restrict users from forwarding messages only to addresses within our domain, so that no one can forward mail to private email accounts. What is the simplest way to do this in Zimbra version 10.1.10?

You would probably need to implement CBPolicyD with custom rules.