Go to the Vacation Mail page. There, you can enter the Subject and the text for the message you'd like us to send to your correspondents. When you click "On", you will see the option to schedule when we start sending the message, and when we will stop sending it.
If you do not provide a start and stop date, we will start sending it immediately, and stop when you come back to turn it off. If you want to turn off Vacation Mail earlier than your end date, just come back and click the button marked "Off".