The best Calendar alternative to Microsoft Outlook is Thunderbird, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 100 alternatives to Microsoft Outlook and loads of them are Calendar Apps so hopefully you can find a suitable replacement. Other interesting Calendar App alternatives to Microsoft Outlook are Evolution, eM Client, Betterbird and Spark Mail.
Cross-platform email client supporting multiple identities, chat, and strong filtering. Extend functionality with add-ons like RSS/Atom feed readers and PGP support.
Evolution is a personal information management application that provides integrated mail, calendaring, address book and task list functionality.
eM Client is a full featured e-mail client with a modern and easy to use interface. eM Client also offers calendar, tasks, contacts, notes and chat.
Betterbird, a soft fork of Mozilla Thunderbird, improves user experience with advanced features, bug fixes, security patches, and multi-row descriptions similar to Outlook. Compatible with multiple platforms and can be used alongside Thunderbird, sharing the same profile.
E-mail app with all the great features: swipes (long/short), snooze, add (multiple) attachments from the cloud, support for various e-mail services and more.
Email and news client on GTK+ foundation featuring quick performance, extensible plugins, secure protocols, advanced filtering, strong folder and contact management, lightweight design, powerful search, customizable interface, multi-language support, and encryption.
Canary can write your emails, prioritize what needs attention, silence spam & much more. Say hello to your Inbox Copilot!
The powerful, full-featured Personal Information Manager for Windows offering Email, Synchronization, Portability, Network support, Android and iOS versions.
Keep track of your busy schedule and share it with others using Calendar. Create separate calendars — one for home, another for school, a third for work, and so on. See all your calendars in a single window or choose to see only the calendars you want.
The free Zimbra Desktop client allows you to meld the online and offline worlds – storing and synching your email, calendar, contacts, files and documents in the cloud, yet having them locally accessible when on the road.
Foxmail is a free POP3 and IMAP4 e-mail client in English and Chinese for Windows systems.
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Despite its age, Thunderbird remains the most fully featured email client out there. Various add-ons can extend its functionality, it (now) has a built in calendar and, unlike Outlook, it's free, open source and respects your privacy.