The Fallback to the Internet for updating the Definitions when a Device it out-of-office, is defined by the “Definition Update Sources” in the Antimalware Policy. The Chance that you run into the exact same error is pretty small, however I still wanted to share the Solution. I recently had an interesting Problem, regarding the Definition Update Fallback to the Internet on Windows 10 Devices with a managed Windows Defender using ConfigMgr.
