Mailbird is a desktop email client for Windows 7, 8 and 10. Developed by Mailbird
License: Freemium
Apps available for Windows
Zimbra Desktop is an offline client that lets you manage various email accounts in one desktop tool. Developed by Zimbra
License: Free Personal
Apps available for Mac OS X Windows Linux
Mailbird is a paid, user-friendly email client with extensive integrations and a focus on customization, while Zimbra Desktop is an open-source, robust email client suited for collaboration and flexibility, albeit with a steeper learning curve.