This feature is also known as an out-of-office auto-reply message. You can set a message that automatically replies to people who send you messages when you are out of the office for an extended period of time.
Multiple emails are from the same address receive an auto-reply message once a week.
Go to Preferences and select Mail.
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 June 1, 2010."
Set the start and end dates for sending the away message.
Click Save.