Thunderbird - Thunderbird is a free email application that's easy to set up and customize - and it's loaded with great features!

Evercontact - Your contacts always up to date and automatically with Evercontact.

Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.

CONTACTBOX - CONTACTBOX combines the simplicity of an address book with effective functions of a CRM system.

eM Client - eM Client is a fully-featured email client for Windows and macOS with a clean and easy-to-use interface. eM Client also offers features for calendars, tasks, contacts, notes, and chat.

Bigin by Zoho CRM - Pipeline-centric CRM built and priced for small businesses