1. On your computer, open Gmail.
  2. In the top right, click Settings Settings and then See all settings.
  3. Scroll down to the "Vacation responder" section.
  4. Select Vacation responder on.
  5. Fill in the date range, subject, and message.
  6. Under your message, check the box if you only want your contacts to see your vacation reply.
  7. At the bottom of the page, click Save Changes.
Note: If you have a Gmail signature, it will be shown at the bottom of your vacation response.


More info (including a video) available at Create a vacation reply - Computer - Gmail Help (google.com)