I want to block any email send from the accounts under the domain internal.mydomain.com that are sent to any any external email. Example:
Sender -> Receiver -> Result
john@mydomain.com -> peter@mydomain.com -> OK
john@mydomain.com -> peter@internal.mydomain.com -> OK
john@mydomain.com -> peter@sales.mydomain.com -> OK
john@mydomain.com -> peter@gmail.com -> OK
john@internal.mydomain.com -> peter@mydomain.com -> OK
john@internal.mydomain.com -> peter@internal.mydomain.com -> OK
john@internal.mydomain.com -> peter@sales.mydomain.com -> OK
john@internal.mydomain.com -> peter@gmail.com -> BLOCKED
how can I achieve that?