Electronic mail is a method of transmitting and receiving messages using electronic devices. It was conceived in the late–20th century as the digital version of, or counterpart to, mail. Email is a ubiquitous and very widely used communication medium; in current use, an email address is often treated as a basic and necessary part of many processes in business, commerce, government, education, entertainment, and other spheres of daily life in most countries.
In computing, the Post Office Protocol (POP) is an application-layer Internet standard protocol used by e-mail clients to retrieve e-mail from a mail server. Today, POP version 3 (POP3) is the most commonly used version. Together with IMAP, it is one of the most common protocols for email retrieval.
An email client, email reader or, more formally, message user agent (MUA) or mail user agent is a computer program used to access and manage a user's email.
The Maildir e-mail format is a common way of storing email messages in which each message is stored in a separate file with a unique name, and each mail folder is a file system directory. The local file system handles file locking as messages are added, moved and deleted. A major design goal of Maildir is to eliminate the need for program code to handle file locking and unlocking.
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 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, web browsing, and RSS news aggregation.
The following tables compare general and technical features of notable email client programs.
Kolab is a free and open source groupware suite. It consists of the Kolab server and a wide variety of Kolab clients, including KDE PIM-Suite Kontact, Roundcube web frontend, Mozilla Thunderbird and Mozilla Lightning with SyncKolab extension and Microsoft Outlook with proprietary Kolab-Connector PlugIns.
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.
Push email is an email system that provides an always-on capability, in which when new email arrives at the mail delivery agent (MDA), it is immediately, actively transferred (pushed) by the MDA to the mail user agent (MUA), also called the email client, so that the end-user can see incoming email immediately. This is in contrast with systems that check for new incoming mail every so often, on a schedule. Email clients include smartphones and, less strictly, IMAP personal computer mail applications.
The comparison of mail servers covers mail transfer agents (MTAs), mail delivery agents, and other computer software that provide e-mail services.
Jami is a SIP-compatible distributed peer-to-peer softphone and SIP-based instant messenger for Linux, Microsoft Windows, macOS, iOS, and Android. Jami was developed and maintained by the Canadian company Savoir-faire Linux, and with the help of a global community of users and contributors, Jami positions itself as a potential free Skype replacement.
eM Client is a desktop email client for Windows and macOS. It features sending and receiving email, managing calendars, tasks, contacts, and notes, and XMPP-based communicators. It was originally released in 2007 and still receives regular updates as of August 2023. Versions for Android and iOS were released for beta testing in 2023.
OfflineIMAP is IMAP synchronization utility software, capable of synchronizing mail on IMAP server with local Maildir folder or another server.
Tor Mail was a Tor hidden service that went offline in August 2013 after an FBI raid on Freedom Hosting. The service allowed users to send and receive email anonymously to email addresses inside and outside the Tor network.
Mailbird is a desktop email client for Microsoft Windows, compatible with Windows 7 and all later versions. As well as sending and receiving emails, Mailbird includes managing calendar events and contacts from different email providers, social media, task management, file share, and video-conferencing integrations. Mailbird is offered via paid subscription, but also includes a free version.
K-9 Mail is free and open source email client for Android. It is designed as an alternative to the stock email clients included with the platform; it supports both POP3 and IMAP protocols and supports IMAP IDLE for real-time notifications. The project is named after the Doctor Who character K9.
The JSON Meta Application Protocol (JMAP) is a set of related open Internet Standard protocols for handling email. JMAP is implemented using JSON APIs over HTTP and has been developed as an alternative to IMAP/SMTP and proprietary email APIs such as Gmail and Outlook. Additional protocols and data models being built on top of the core of JMAP for handling contacts and calendar synchronization are meant to be potential replacements for CardDAV and CalDAV, and other support is currently in the works.
Mail-in-a-Box is a free and open-source program for mail server hosting developed by Joshua Tauberer. The software's goal is to enable any user to turn a cloud system into a mail server in few hours. The tool enables developers to host mail for multiple users and multiple domain names.
