To use Rewind with Gmail, set your default mail reader to Google Chrome before proceeding to install the service handler.
1. Set default mail reader to Google Chrome
Open the Mail app.
Click on the Mail menu from the top toolbar, and click Settings.
Click on the General tab.
Set the Default email reader to Google Chrome.
2. Install service handler in Chrome for Gmail
Go to chrome://settings/handlers and make sure the toggle is on "Sites can ask to handle protocols".
Go to http://gmail.com and login with your account.
On the right side of the address bar click on the squares with a circle handlers icon to the left of the star icons.
Click Allow on the popup box.
Gmail should now open in Chrome by default for all mail links.
Your chrome://settings/handlers page should now have gmail listed under 'email'.