Follow steps as below to setup auto responder.
1) Log into your gmail account.
2) Click on ‘Settings’ link in your gmail home page at the top-left. (Last but one link to ‘Sign-out’ link).
3) In ‘Settings’ page you can find ‘Vacation Responder’ section. By default Vacation Responder will be off.
a) Click on ‘Vacation Responder On’
b) Enter first day and End day, during which you want to send vacation responder.
c) Enter Subject, which will act as subject to your vacation responder.
d) Enter Message that you want to convey. May be saying ‘I am in vaction now, will get back to you as soon as I am in’.
c) Optionally you have an option to send Vacation Responder to only contacts in your inbox by checking the check box, below message edit box. Otherwise Vacation responder will be sent to every mail you receive.
Thats it all set go enjoy your vacation :):)