The best alternative to Microsoft Outlook is eM Client, which is free. If that doesn't suit you, our users have ranked more than 100 alternatives to Microsoft Outlook and many of them are so hopefully you can find a suitable replacement. Other interesting alternatives to Microsoft Outlook are Betterbird, FairEmail, Kontact and EssentialPIM.
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.
Supports 365 Shared Mailboxes.
One of the only fully integrated email and calendar solutions that supports Office365, Exchange, Outlook, Gmail, GSuite, POP, and IMAP. Good performance and usability.
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.
open source, secure, regularly updated
The powerful, full-featured Personal Information Manager for Windows offering Email, Synchronization, Portability, Network support, Android and iOS versions.
Tricky to configure. Does not speak MAPI, but many Cloudservices. I was not successful to synchronize OwnCloud
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.
This is a very integrated suite of programs offering all the functionality of Outlook. Native to KDE's Plasma desktop environment.
Amie is a productivity application that facilitates task, event, and contact management, integrating a scheduling feature for task and event time allocation, and effectively transforming the calendar into a todo list, with color-coding for improved organization and visual...
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.
Outlook is an all-in-one solution including mail calendar etc. this soft does only one thing
The open source cloud with LibreOffice online - LibreOffice online + Seafile + KDE. Improve your productivity and communicate better with your team members. The world is moving forward. Welcome to the open source cloud!.
Popular calendar app integrating Google, Live, Outlook, iCloud, Exchange, Office365, and Facebook into an easy overview. Manage appointments, events, and birthdays seamlessly with customizable views and notifications. Optimized for both personal and professional use.
AquaMail is an email app for Internet and Exchange mail, for Android 4.0.3 and higher.
Czechia
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Bulgaria
It is not very overcomplicated! Very simple, but functional design. therefore also very easy to set up and use.