The original manual won't work, because the step of configure the plugin is missing AND the original plugin only support fixed addresses and no networks.
Replaced roundcube-dovecot_client_ip with fork (with CIDR support)
Added important configuration step to add trusted proxies (without this step it wont work!)
The original manual won't work, because the step of configure the plugin is missing AND the original plugin only support fixed addresses and no networks.