This will walk you through the process of setting up a vacation message through the Outlook Web Application (OWA).
Once logged into OWA, select Set Automatic Replies From the options menu.
Turn on Automatic Replies by selecting the Send automatic reply radial button.
Select a start time and date to begin the automatic reply.
Select an end time and date.
Type your vacation message in the text box.
When you are done setting up your vacation message, press the save button in the lower right corner of the screen.