While restricting access to the Internet for all computers, Outlook needs to be the only app allowed.
PCs connected to Kerio Control should not be able to browse the Internet.
This article provides information on how to restrict Internet access and allow only Outlook for certain IP addresses using Content Filter rules.
In Kerio Control Webadmin navigate to Content Filter and create a new Content Rule for Outlook and Outlook Express categories with action = Allow and source = IP address group. In this case, DHCP Clients = 192.168.0.11 - 192.168.0.254 (current DHCP range).
Add the second rule to block other content:
Detected Content: Any
Source: same IP address group
Optionally, create a third content rule to allow content for specific DHCP clients IP address group (important employees, network devices, etc).
Important: these IP addresses should be reserved by Mac address.