GNOME Evolution is the official personal information manager for GNOME. It has been an official part of GNOME since Evolution 2.0 was included with the GNOME 2.8 release in September 2004. It combines e-mail, address book, calendar, task list and note-taking features. Its user interface and functionality is similar to Microsoft Outlook. Evolution is free software licensed under the terms of the GNU Lesser General Public License (LGPL).
Microsoft Outlook is a personal information manager software system from Microsoft, available as a part of the Microsoft Office and Microsoft 365 software suites. Though primarily being popular as an email client for businesses, Outlook also includes functions such as calendaring, task managing, contact managing, note-taking, journal logging and web browsing.
SOGo is an open source collaborative software (groupware) server with a focus on simplicity and scalability.
Kontact is a personal information manager and groupware software suite developed by KDE. It supports calendars, contacts, notes, to-do lists, news, and email. It offers a number of inter-changeable graphical UIs all built on top of a common core.
Calendaring Extensions to WebDAV, or CalDAV, is an Internet standard allowing a client to access and manage calendar data along with the ability to schedule meetings with users on the same or on remote servers. It lets multiple users in different locations share, search and synchronize calendar data. It extends the WebDAV specification and uses the iCalendar format for the calendar data. The access protocol is defined by RFC 4791. Extensions to CalDAV for scheduling are standardized as RFC 6638. The protocol is used by many important open-source applications.
The following tables compare general and technical features of notable email client programs.
Roundcube is a web-based IMAP email client. Roundcube's most prominent feature is the pervasive use of Ajax technology. Roundcube is free and open-source software subject to the terms of the GNU General Public License (GPL-3.0-or-later), with exceptions for skins and plugins.
Group-Office is a PHP based dual license commercial/open source groupware and CRM and DMS product developed by the Dutch company Intermesh. The open source version, Group-Office Community, is licensed under the AGPL, and is available via SourceForge. GroupOffice Professional is a commercial product and offers additionally mobile synchronisation, project management and time tracking.
Bynari is a defunct company based in Dallas, developing server and email software, mainly known for its Insight Family, similar to Microsoft Exchange Server with Outlook.
EGroupware is free open-source groupware software intended for businesses from small to enterprises. Its primary functions allow users to manage contacts, appointments, projects and to-do lists. The project releases its software under the terms of GNU General Public License (GPL).
Zarafa was an open-source groupware application that originated in the city of Delft in the Netherlands. The company that developed Zarafa, previously known as Connectux, is also called Zarafa. The Zarafa groupware provided email storage on the server side and offered its own Ajax-based mail client called WebAccess and a HTML5-based, WebApp. Advanced features were available in commercially supported versions. Zarafa has been superseded by Kopano.
Ipswitch IMail Server is an email server application with groupware functionality that runs on Microsoft Windows OS. It was developed in 1994 by Ipswitch, Inc., a software company based in Lexington, Massachusetts.
vCard Extensions to WebDAV (CardDAV) is an address book client/server protocol designed to allow users to access and share contact data on a server.
GroupWise is a messaging and collaboration platform from Micro Focus that supports email, calendaring, personal information management, instant messaging, and document management. The GroupWise platform consists of desktop client software, which is available for Windows,, and the server software, which is supported on Windows Server and Linux.
MailSite is a commercial mail server, calendar software, contact manager and collaborative software that was developed by Rockliffe Systems. It was one of the first mail servers to run on Windows NT using Internet standards when version 1.2 was released in 1996. Additionally, MailSite has been in continual development since 1996 with version 10 released in 2013, and runs on a single Windows Server as well as on a cluster of Windows Server computers. MailSite works natively with Microsoft Outlook versions 2007 to 2013 for mail, calendar and contacts without requiring any Outlook plug-ins, as well as including an Exchange ActiveSync (EAS) server for synchronizing mail, calendar and contacts with mobile devices. MailSite also works with Internet Standards-based mail clients such as Mozilla Thunderbird.
Kolab Now is a web-based email and groupware service, based completely on free and open-source software. It is owned and operated by Kolab Systems AG and was formerly known as MyKolab.
Kopano is an open-source groupware application suite originally based on Zarafa. The initial version of Kopano Core (KC) was forked from the then-current release of Zarafa Collaboration Platform, and superseded ZCP in terms of lineage as ZCP switched to maintenance mode with patches flowing from KC. Kopano WebApp similarly descended from Zarafa WebApp. Since October 2017, Kopano Core is also known more specifically as Kopano Groupware Core, since Kopano B.V. developed more products that were not directly requiring groupware components.
