You can no longer set your out of office through Outlook. It now needs to be done through the online interface.
Log in to http://mail.oakgrove.school and go to 'Settings' in the top right by clicking the Gear followed by Settings
On the General tab, scroll down to the bottom where you'll see the settings for Out of office AutoReply
Here, you can enable out of office, set a start and end date along with a custom subject and message.
NOTE, you can no longer send a different out of office to internal and external people.
When done, click Save Changes
When the Out of Office is active, you'll see a yellow bar at the top