Try RMail PRE-Crime Services – Installing the RMail app for Gmail extension in your Chrome browser
Follow these steps to install the RMail extension for Gmail in your Chrome browser.
1. Make sure you are using Chrome browser (non-mobile version) to install and use RMail app for Gmail.
2. Go to the official Chrome Store page for RPost for Gmail
3. Click on the Add to Chrome button on the Chrome Store page. A dialog window will open, listing the permissions the app will need. Click on Add Extension.
4. Log into your Gmail account to activate and begin using the extension.
5. Once installed, simply click the Compose button. The Send Registered button and RMail features options will then appear at the bottom of your Gmail New Message window, along with the gear icon to access your settings, as shown in the screenshot below.
Read the following article to learn how to remove the RMail app for Gmail extension from your Chrome browser