After upgrading Sametime to V12.0.2 you cannot send messages to offline users

After upgrading to Sametime V12.0.2, we cannot send chats to offline users anymore using client or mobile app. After opening a case, HCL told us that there should be a policy for that. But this policy doesn't exists in ../sametime-config/policy/policies.user.xml.
This is a companion discussion topic for the original entry at https://www.angioni.nl/2024/05/04/after-upgrading-sametime-to-v12-0-2-you-cannot-send-messages-to-offline-users/