Please follow these steps to install the RMail extension for Gmail in your Chrome browser.
Make sure you are using Chrome browser before proceeding Note: You must be using Chrome browser (non-mobile version) to install and use RMail for Gmail.
Click the Add to Chrome button below to go to the official Chrome Store page for RMail for Gmail.
Click the “Add to Chrome” button on the Chrome Store page. A dialog window will open, listing the permissions the app will need. Click Add Extension.
Log into your Gmail account to activate and begin using the extension
Once installed, just hit the Compose button and the RMail features and settings options will appear in the bottom of your Gmail New Message window, as shown in the screenshot below
The link to the Chrome Store page is also listed here.