Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.
24me - Next Generation Personal Assistant
Thunderbird - Thunderbird is a free email application that's easy to set up and customize - and it's loaded with great features!
Awesome Cal - Awesome Cal is a Calendar application for your iPhone that you can take anywhere and keep close by to monitor all the upcoming birthdays, festivities, meetings, and more from a single place.
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.
Calvetica - The fast calendar for iPhone. Add an event in just two quick taps.