Sign in Outlook Web App (OWA), click "Options" at the upper right corner, and select "Set Automatic Replies..." from the drop down list.
Under "Automatic Replies", the default option is "Don't send automatic replies" and the rest of screen is grayed out.
Click "Send automatic replies" option and then:
Determine whether you want the auto reply to be sent to people outside of the university.
If yes, decide whether you want only the people in your Contacts lists to receive the message or anybody who email you in that period. Compose a different message (or copy and paste from above), then click "Save" button.
A "Saving the Information..." box appears to indicate the process, once it disappears, click "My Mail" in the upper right corner to go back to Inbox. An auto reply will be sent to people who email you during the period you defined.