3) eM Client

This isn’t a program that’s been specifically designed for Gmail, like Kiwi or Mimestream, but it’s an excellent, all-round program that will capably handle your Gmail inbox and any of the other inboxes you want to plug into it. It’s available for Windows and macOS, and it’s free for personal use for up to two email accounts.
You’ve got options covering everything from encryption, to the color scheme of the interface, to whether or not you want emails synced for offline access (handy if you know you’re going to be traveling). Getting your Gmail account connected is really straightforward, too, and only takes a few seconds.
Key Gmail features from the web interface are carried over, including the option to snooze emails and bring back messages that you’ve just sent, plus support for labels (which are called tags inside the eM Client interface)—and you can integrate the app with your calendars and contacts as well if you need to.
Download eM Client for Windows or macOS. There’s a free version, a $59.95 Pro version, and a $250 Business Pro option, both one-time payments.