You can use automatic replies if you are away from work, on holiday or sick leave and unable to respond to email. 

1. In Outlook for the Web, click on the Settings cog and select View all Outlook settings

2. Go to Automatic Replies

3. Enable Turn on automatic replies

4. Enter the message you want for your automatic reply in the text box for inside and outside your organisation. If you want to choose a time period of your message, select this here as well

5. Click Save when done