Open the Email Server Settings from Settings > Configuration > Email Server Settings  - you will see a form like the one shown below:

• Select Office365 from the drop-down list

• Enter your email address and press Save Changes
• Then press Authorise Office365

You will then be taken through the steps to authorise your Office 365 account - when this has been successfully done you will see a message 'Office365 Connection successfully completed'

• Click Save Changes
• Optionally you can press the 'Send Test Email' button to check your settings are correct - this will send an email to the email address you entered.