Wmail is an open-source Chromium-based Gmail client for Windows, OS X and Linux.
The program supports both Gmail and Google Inbox accounts, and you can add and manage as many as you need.
You could do this with a browser, of course, but Wmail gives you much improved support for drag and drop and keyboard shortcuts, as well as providing native desktop notifications when a new message arrives.
Performance is better, too – no multiple tabs or waiting for pages to load – and the package is built around some quality open-source components (Chromium, FFmpeg).
Other features include spellchecking, a system tray icon, and an “Unread” badge showing you at a glance how many emails are waiting for your attention.
Early Wmail builds had plenty of issues (particularly with notifications) and limited options and settings, but recent updates have addressed many of these and the latest editions are much more usable. If you had problems with a pre-May build, take another look.
Wmail is available for Windows 7 and later, OS X and Linux.