Webmail
1. Login via http://portal.office.com
2. Select Options from top menu
3. Turn on Automatic Replies



iPhone
1. Settings
2. Mail, Contacts, Calendars
3. Select the email account
4. At the bottom of the account page turn Automatic Reply on and enter your message.



Blackberry OS 10
While viewing the BlackBerry Hub, tap : for more options
Tap Settings followed by Email Accounts
Tap the desired email account
Set the Out of Office Reply switch to On
Type a message
Tap Back when finished to save your changes



Outlook 2007, 2010, 2013
Refer to - KB290846