The G Suite Marketplace offers a wide range of quality enterprise apps that add functionality and features to native Google Cloud apps. Mailmeteor is a verified G Suite add-on, to use Mailmeteor you need to install it first on your Google account.
Click on the "Install" button.
A consent popup appears, click on "Continue".
Choose the account on which you want to install Mailmeteor.
Review permissions and click on "Allow"
Mailmeteor has been installed! Click on "Done".