Download Gmail add-on: https://goo.gl/JFwuZZ
Autoresponder Tutorial: http://labnol.org/?p=28980
Send pre-written email replies to your Gmail messages from anywhere including the mobile apps of Gmail. You can include attachments in your canned responses and it is possible to auto-reply to multiple emails in one go with a Gmail draft template.
Download add-on: https://goo.gl/JFwuZZ