Automatically exported from code.google.com/p/gmail-delay-send
Installation How-to copied from the above page: How to install
Gmail Delay Send 8.0 has a much easier installation process than prior versions. Please follow the steps below:
Visit this page and accept the authentication requests.
Select Enable -> On.
Click the 'Save preferences' button.
NOTE: Whenever you want to change the options that you've set, revisit the link above.
That's it!