1. Login to your gmail account.
2. Click on the settings in the right corner as shown.
3. It will drop down a menu,select “Settings” from that as high-lighted in the pic.
4. Then select “General” tab and scroll to bottom you can see a heading named “Vacation responder” turn it on,write your subject and message in the space provided which will be send as replies for incoming mail.
5. Don’t forget to save your changes.