This feature is also known as an out-of-office auto-reply message. You can set a vacation message that automatically replies to people who send you messages when you are out of the office for an extended period of time. That message is sent to each recipient only once, regardless of how many messages that person sends you during the designated vacation period.
Click the Preferences>Mail tab.
In the Receiving Messages section, check Send auto-reply message.
In the text box, enter the message to be sent, such as "I am currently out of the office and am checking voice mail but not email. I will return on August 1, 2009."
Set the start and end dates for using this message.
Click Save. The away message feature is enabled immediately.