Microsoft has announced that automatic activation of out of office (OOF) voicemail greetings based on OOF calendar events will be retired in June 2024. Once retired, TTU enterprise voice users will still have the option to play OOF greetings all the time (that is, when that option is checked) or when you have an OOF auto reply set up in Outlook. This will only retire the option to play the OOF greeting when the status of a calendar item is set to "Out of Office".
The associated setting is located at
https://aka.ms/vmsettings. The setting being retired is labeled "I have an Out of Office calendar appointment".