Thunderbird - Thunderbird is a free email application that's easy to set up and customize - and it's loaded with great features!
Dialpad - Switch is a cloud-based phone system built for Google Apps users.
Mailbird - Mailbird is the best email client for Windows 7, 8 and 10
RingCentral - RingCentral is the leading provider of cloud-based communications and collaboration solutions for small business and enterprise companies
Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.
Aircall - Aircall is a call center software of a new generation designed for fast growing companies. Setup instantly and integrates to your CRMs