> Login to portal.office.com 

> Locate to Outlook.


> Go to the settings cog in the top right hand corner.


> Then go down to 'View all Outlook settings'.


> This pop up box should appear, go down to 'Automatic replies'.


> Once in Automatic replies, it will automatically be turned on, to turn it on toggle the switch to ON.


> Turning on, you can type your Out of Office message into the text box.


> You can also set a start time and an end time, if you would like your Out of Office for certain times.


> By pressing 'Save', if anyone sends you an email then onwards it will send back the Out of Office message you have put.