To get access to Mailbutler's features, you need to install at least one of these extensions for your preferred email application.
By installing this extension for Apple Mail, you get access to all Mailbutler features directly from within the best email application for macOS.
Get access to all Mailbutler features directly from within Gmail when using Chrome as your web browser.
By installing this add-in for Microsoft Outlook, you get access to all Mailbutler features directly from within Outlook.