Form Mule is a Google Spreadsheet add-on that lets you automate emails based on form submissions. It’s powerful and easy to use. Get it here: https://goo.gl/WGvraX
Undo Send & Canned Responses.
NOTE: To actually USE Undo Send, look for the Undo link in the Email Sent confirmation tooltip. The tooltip as a post-it yellow notification at the top of the screen after you send an email.