alternative-to-outlook

src: https://alternativeto.net/software/microsoft-office-outlook/

Alternatives to Microsoft Office Outlook for all platforms with any license
Thunderbird
Thunderbird is a free, open source, cross-platform e-mail, news and instant messaging client. The project strategy is modeled after Mozilla Firefox. It supports POP (storing mail locally on your hard drive so that it can be accessed without an internet connection), and IMAP. It features excellent mail filter capabilities and management. Thunderbird has strong support for using multiple accounts and identities, including automated signature features.

Seems to be more secure than Microsoft alternatives and more easily updatable.
Guest • Apr 2017 • 9 agrees and 4 disagrees
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.
JohnFastman • Jan 2017 • 10 agrees and 8 disagrees
For me it is the only alternative to Outlook, if you want power of Outlook and open source there is just no other app.
wookahn624 • Jun 2018 • 1 agrees and 1 disagrees
Free Open Source  Mac Windows Linux BSD PortableApps.com ... Extensible by Plugins/Extensions Built-in RSS reader Support for IMAP Multiple Account support ...
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Message write window
Mail account setup
Message search
Add-ons Manager
Address book
About Thunderbird window
K-9 Mail
K-9 is an open source email client for Android with multi-folder sync, email signatures, Bcc-to-self, return-address configuration, keyboard shortcuts, Exchange Support, message flagging, IMAP deletes, saving attachments, configurable notifications and more.

Not the prettiest, but it's open source (trustworthy), free, privacy-respecting and very functional. My go-to Android email client. I cannot hesitate less in recommending it.
JohnFastman • Jan 2017 • 3 agrees and 0 disagrees
Deletes e-mail from the server even when underground in NYC subway. Makes life so easy to delete e-mails while on the train When surfacing, K-9 syncs with the server and POOF....those unwanted e-mails are gone from the server.
Online_Purchases1 • Feb 2017
Free Open Source  Android Android Tablet Ad-free Configurable Encrypted chat Multiple Account support ...
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Mailbird
Mailbird is a Windows based email client which design and style match Windows 7, 8 and XP’s native styles. Mailbird provides clean, simple and lightning fast email experience. The current free version of Mailbird has Multi Account support for Gmail, Yahoo, Outlook.com, iCloud, and any other IMAP/POP3 email provider. S/MIME and PGP are not supported.

Not enough functionality. No smart attachment feature, no quick sort by address or flags or attachments etc. Not really a business email client
Guest • Nov 2018 • 0 agrees and 1 disagrees
Freemium $ $ $  Windows Undo send Asana integration Sync Contacts Dropbox integration ...
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eM Client
eM Client is a full featured email client with a modern and easy to use interface. - offers calendar, tasks, contacts and even chat. - supports all major services including Gmail, Exchange, iCloud, and Outlook.com. - easily imports your data from most of the other e-mail clients. This includes Microsoft Outlook, Outlook Express, Windows Mail, Windows Live Mail, Thunderbird, The Bat and more. - fully supports touch devices like touch-enabled laptops, tablets and hybrid devices.

A nicer, less cluttered version of outlook. Biggest advantage is ease of navigation and use. E.g. you can view all mail and calendars in a single combined view, without tampering with any settings. Similarly, the tasks view is also very capable. Added to this, the support team are very responsive and helpful.
logicbrick • Nov 2017 • 2 agrees and 3 disagrees
Freemium  Mac Windows Calendar integration Automatic Backup Built-in themes Built-in translation ...
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Evolution
Evolution is the official personal information manager and workgroup information management tool for GNOME. It combines e-mail, calendar, address book, and task list management functions. Features E-mail retrieval with the POP and IMAP protocols and e-mail transmission with SMTP. Secure network connections encrypted with SSL, TLS and STARTTLS. E-mail encryption with GnuPG and S/MIME. E-mail filters.

Support for EWS allows me to connect to exchange and get all the benefits like contacts and calendar I wouldn't so easily get on Thunderbird. Also it nicely integrates with the built in Ubuntu calendar as well which is a big plus.
Guest • Jul 2018 • 1 agrees and 1 disagrees
Fast and User friendly. Light-weight and classic menus really give a touch of old classic office 2003. Easy integration of mails especially exchange mails without facing any bottlenecks.
Guest • Sep 2018
Free Open Source  Linux BSD S/MIME GNOME OpenPGP CalDAV Calendar integration Built-in RSS reader CardDAV ...
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Apple Mail
Apple Mail changes the way you interact with your email every day. Mail displays your messages and open email side by side in a widescreen, two-column view. The favorites bar below the toolbar works much like a bookmarks bar in a web browser, giving you one-click access to your mail folders. A compact preview of each message — including the first two lines — lets you scan your messages at a glance.

Outlook is an all-in-one solution including mail calendar etc. this soft does only one thing
Guest • Oct 2015 • 7 agrees and 10 disagrees
Free  Mac iPhone iPad CalDAV CardDAV Encrypted email Bundled with macOS Add a feature
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Spark
Smart Inbox automatically detects if an email is personal, a notification or a newsletter and groups it with similar emails for easy batch processing using beloved swipes. With just a glance, you can see if emails are important or just a product announcement from a service you've never used. We all love the feeling of accomplishment when we have finally dealt with our inbox. Spark makes this easy to achieve. Quickly process your emails, swiping to archive or delete as necessary.

Free  Mac iPhone iPad Apple Watch Calendar integration Cloud sync Configurable Configurable request timeout ...
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OpenProject
OpenProject is an open source software for project management with a wide set of features and plugins and an active international community. It supports project timelines / Gantt charts, issue tracking, wiki, document management, time and cost reporting, code management, Scrum and much more.

Freemium $ $ $ Open Source  Web Self-Hosted Ruby Cloudron Kanban boards Computer-aided machining (CAM) Cost Calculator Cost estimate ...
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Postbox
Postbox is an email application that helps you organize your work life and get stuff done. It has all the elegance and simplicity of Apple Mail, but with more power and flexibility to manage even the most demanding workloads. Key Features * Ultra-Fast Search - Instantly find messages, attachments, images, links, and contacts. * Conversation Views - Make sense of email threads through chronological message views.

Commercial  Mac Windows Multiple Account support Box.com integration Built-in RSS reader Dropbox integration ...
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Claws Mail
Claws Mail is an email client (and news reader), based on GTK+, featuring Quick response Graceful, and sophisticated interface Easy configuration, intuitive operation Abundant features Extensibility Robustness and stability

Free Open Source  Windows Linux BSD Lightweight Built-in RSS reader Content Filtering Customizable ...
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Mailspring
Mailspring is a desktop email client designed for macOS High Sierra, Windows 10 and Linux. With modern features like unified inbox, snoozing, templates, offline search, and support for Gmail labels, Mailspring will breathe life back into your tired inbox! Mailspring is free and supports all IMAP providers, including Gmail, Office 365 and iCloud. Mailspring does not support Exchange ActiveSync.

Freemium $ $ $  Mac Windows Linux Arch Linux Fedora ... Multiple Account support Night mode/Dark Theme Unified inbox Customizable ...
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Geary
Geary is a lightweight email program designed around conversations and built for the GNOME desktop. It's designed to let you read your email quickly and effortlessly. Its interface is based on conversations, so you can easily read an entire discussion without having to click from message to message. Geary is written in Vala .

Free Open Source  Linux BSD GNOME Multiple Account support Add a feature
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Opera Mail
Opera Mail powerfully organizes, indexes, and sorts your messages. It has spam filtering (both automated and Bayesian), supports POP3 and IMAP, newsgroups as well as Atom and RSS feeds. Opera Mail uses one database that keeps an index of all mail, and sorts the messages automatically into several "views" or accesspoints. Messages are automatically sorted by type, such as mailing lists, and mail with attachments . This approach to indexing allows for quicker access to messages.

Discontinued Opera Mail is no longer updated and supported, but last version, 1.0.1044, released in February 2016, can be still downloaded from the official website.
Free  Mac Windows PortableApps.com Built-in RSS reader Integrated Spam Protection Mail filtering Message Filtering ...
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Mutt
Mutt is a small but very powerful text-based mail client for Unix operating systems. Some of its features are: color support, message threading, MIME support (including RFC2047 support for encoded headers), PGP/MIME (RFC2015), various features to support mailing lists, including list-reply, active development community, POP3 support, IMAP support.

Powerful configuration is possible with mutt, and vim in the terminal.
scholasticphilosopher • Mar 2018 • 0 agrees and 2 disagrees
Free Open Source  Mac Windows Linux Xfce Command line interface Support for IMAP POP3 Support S/MIME support Add a feature
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Airmail
Airmail is a lightweight and lightning fast mail client for Mac. Feature list: Accounts: - Unified Inbox and folders - Multi Account with editable html signatures. - Aliases management with custom SMPT - Support for Gmail, GoogleTM Apps, iCloudTM, Yahoo!, AOL and Generic IMAP.

Commercial  Mac iPhone iPad Apple Watch Customizable Dropbox integration Fullscreen support Lightweight ...
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Open365
Open365 is an Open Source, self-hosted file sync and cloud apps platform including a full LibreOffice Online. You can also access your email, calendar and contacts using KDE Kontact. Everything is accessible from a simple webpage using any HTML5 browser.

Discontinued The project seems to be no longer developed. Last commit on the GitHub repo was made on June 27th, 2016, but it can be still downloaded and installed.
Free Open Source  Android Self-Hosted Cloud sync Add a feature
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Kontact - KMail
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. It uses KParts to embed the various applications (KMail, KAddressBook, Akregator, etc.) into the container application.

Free Open Source  Mac Windows Linux BSD No features added Add a feature
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Sylpheed
Sylpheed is a simple, lightweight but featureful, and easy-to-use e-mail client (mailer, MUA). Sylpheed runs on many systems such as Windows, Linux, BSD, Mac OS X and other Unix-like systems. Sylpheed uses GTK+ GUI toolkit. The newest version of Sylpheed works with GTK+ 2.4 or later (2.6 or later is recommended). Sylpheed is a free software distributed under the GNU GPL (the library part is GNU LGPL). You can freely use, modify and redistribute it under the license.

Free Open Source  Mac Windows Linux BSD PortableApps.com Lightweight Add a feature
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Microsoft Mail and Calendar
Windows 10 has Mail and Calendar apps already built in. With the Mail application you can now easily see all message from your favorite people, more clearly organize social updates and newsletters, and use the popular “Sweep” feature to clean up your inbox.

Bundled in win 10 and very simple to use. Great if you just read mail.
Guest • Jun 2017 • 0 agrees and 1 disagrees
Free  Windows Windows S Email tracking Bundled with Windows Add a feature
Microsoft Mail and Calendar icon
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EssentialPIM
EssentialPIM lets you manage appointments, tasks, notes, contacts, password entries and email messages across multiple devices and cloud applications. PIM stands for Personal Information Manager, and it allows you to keep all you information in electronic form. All your appointments, tasks, to do lists, notes and contacts are stored in a graphical and easily accessible form.

Tricky to configure. Does not speak MAPI, but many Cloudservices. I was not successful to synchronize OwnCloud
Guest • Dec 2016
Freemium $ $ $  Windows Android iPhone Portable Add a feature
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Hiri
Fast, good looking email client. Lighter than MS Outlook with some unique and clever features. You can use Hiri to connect to Exchange, Office365, or a Microsoft email account (Outlook.com, Live, Hotmail). Other email providers, such as Gmail, Yahoo, etc are currently not supported. Basics: - Fully integrated calendar - Tasks - Contacts - Built for Exchange, Office 365 and Outlook.com - Uses Microsoft's own protocol - EWS.

Most of the clients listed do not have calendars or tasks. Hiri has it all and works really well with Office 365
kevkav • Jan 2017 • 1 agrees and 0 disagrees
I like how it helps our company to be more productive and focused on tasks. Th UI/UX is much better than Outlook
aleksandarbibovski • Jan 2017
Commercial $ $ $  Mac Windows Linux Calendar integration Office 365 integration Convert Email to Task Add a feature
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The Bat
The Bat! is a secure email client software, built to protect your correspondence against third-parties. The Bat! protects your information through multiple encryption streams with the options to encrypt your emails on disk and during communication through an SSL/TLS connection. Free of global email providers that keep your messages in the cloud, and free of Web clients, The Bat! ensures your data stays private.

Commercial  Windows S/MIME OpenPGP Built-in RSS reader Support for IMAP POP3 Support Portable Add a feature
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Kontact
Kontact is the integrated Personal Information Manager of KDE. Kontact suite unites mature and proven KDE PIM applications under one roof. Thanks to the powerful KPart technology, existing applications are seamlessly integrated into one. The components of KDE Kontact are tailored to work well with each other. This results in features like intuitive drag-and-drop between appointment handling, task lists and contacts. KDE Kontact supports various groupware servers.

Free Open Source  Windows Linux Convert Email to Task Add a feature
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Polymail
Polymail is the modern email client, redesigned. Master your inbox with the most powerful email productivity tools — Email Tracking, Read Later, Send Later & more. All from a simple, unified interface. Say goodbye to cluttered browser add-ons and hello to beautiful email productivity. - Unlimited per-recipient email tracking - know exactly when and by whom your messages are read. - Snooze emails to be read later, when you need them.

Commercial $ $ $  Mac iPhone iPad Sync Contacts Email scheduling Email tracking Multiple Account support Add a feature
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Apple Calendar Good alternative? YES NO
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. Calendar lets you create invitations using information from Contacts, update your guest list, keep track of responses, and receive the latest status information.

It is a calendar not an email app
Guest • Sep 2015
Outlook is an all-in-one solution including mail calendar etc. this soft does only one thing
Guest • Oct 2015 • 2 agrees and 3 disagrees
Free  Mac iPhone iPad iCloud Sync with iCloud Week Planner Add a feature