The best alternative to Evolution is Betterbird, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 50 alternatives to Evolution and 17 are so hopefully you can find a suitable replacement. Other interesting alternatives to Evolution are FairEmail, eM Client, EssentialPIM and KMail.
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.
Open-source, privacy-focused email client offering features such as encryption via OpenPGP and S/MIME, unlimited accounts, a unified inbox, customizable settings, and reformatted emails to prevent phishing. Supports two-way synchronization and provides Pro features for additional customization.
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.
The powerful, full-featured Personal Information Manager for Windows offering Email, Synchronization, Portability, Network support, Android and iOS versions.
KMail is the email component of Kontact, the integrated personal information manager of KDE. Kontact is a personal information manager and groupware software suite for KDE. It supports calendars, contacts, notes, to-do lists, news, and email.
Engineered for iOS, macOS, and watchOS, this fast mail client supports multiple account types, custom actions, Smart Inbox filtering, unified inbox, privacy mode, email scheduling, snooze, third-party app integration, flexible personalization, and advanced workflow tools.
Kontact is just the contacts manager and not an actual mail client. Its mail client is already in the list.
It provides management of events and tasks, alarm notification, web export, network transparent handling of data, group scheduling, import and export of calendar files and more. It is able to work together with a wide variety of calendaring services, including NextCloud, Kolab...
AquaMail is an email app for Internet and Exchange mail, for Android 4.0.3 and higher.
Trojitá, is a fast Qt IMAP e-mail client that respects open standards and facilitates modern technologies. Trojitá values vendor-neutrality that IMAP provides and is committed to be as interoperable as possible.
myMail is the smart email app for managing all your accounts on iOS and Android.
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Betterbird can minimize to tray. And the straightforward native OpenPGP support is excellent.