Top 20 products relevant to Calendar and Email

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

Spark helps you take your inbox under control. Instantly see what’s important and quickly clean up the rest. Spark for Teams allows you to create, discuss, and share email with your colleagues.

Open Source

Spend less time managing your day & more time enjoying it.

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

A simple calendar with events (optional recurring and reminders), week numbers and a customizable...

Open Source

Native email app for email productivity.

Mailbird is the best email client for Windows 7, 8 and 10.

Airmail is a lightweight and lightning fast mail client for Mac.

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. .

freemium

Fantastical, the Mac calendar app you'll enjoy using. Quickly create new events with natural language input and more.

Mailspring is a mail client for Mac, Windows and Linux.

Open Source

Zimbra is trusted by over 500 million users to increase productivity with a complete set of collaboration tools while maintaining total control over security and privacy.

KerioConnect is a commercial mail and groupware server.

There’s big news attached.

Apps/Evolution - GNOME Wiki!

The Power Email App for busy professionals, like you.

Rainlendar - Customizable desktop calendar.

Privacy-aware email app for Mac & iOS.

Claws Mail is an email client (and news reader), based on GTK+, featuring Quick response.

K-9 is an opensource email client making it easy to chew through large volumes of email.