Going on vacation? No access to the Internet? No problem! Use Gmail’s vacation responder to let people know you won’t be able to get back to them right away.
You can set up a vacation response in your Gmail settings that will automatically reply to anyone who emails you. While the vacation responder is enabled, Gmail will send a response to anyone who contacts you.* If that person contacts you again after four days and your vacation responder is still enabled, Gmail will send another vacation response to remind the person that you’re away from your email.
Here’s how to let people know you can’t respond right away:
While the vacation responder is enabled, you’ll see a banner across the top of any Gmail page, displaying the subject of your vacation response. To stop Gmail from automatically sending the response, click end now within the banner. Or, if you’d like to edit the response, click vacation settings.
Keep in mind that your vacation response will start over each time you edit it — if someone receives your initial vacation response, and then emails you again after you’ve edited the subject or body of the message, he or she will receive the edited response, too.
* Messages classified as spam and messages addressed to a mailing list you subscribe to will not receive a vacation response. [source]