Webmail (or web-based email) is any email client implemented as a web application running on a web server. Examples of webmail software are Roundcube and SquirrelMail. Examples of webmail providers are AOL Mail, Gmail, Outlook.com/Hotmail.com and Yahoo! Mail. Many webmail providers also offer email access by a desktop email client using standard email protocols, while many internet service providers provide a webmail client as part of the email service included in their internet service package.
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As with any web application, webmail's main advantage over the use of a desktop email client is the ability to send and receive email anywhere from a web browser. Its main disadvantage is the need to be connected to the Internet while using it. Other software tools also exist to integrate parts of webmail functionality into an OS (e.g. creating messages directly from third party applications via MAPI).
Early implementations
The first Web Mail implementation was developed at CERN in 1993 by Phillip Hallam-Baker as a test of the HTTP protocol stack. This led to the discovery that the specification of the POST method was faulty, requiring the introduction of the Content-Length header. The CERN-PTG daemon was released later that year but was not developed further.
In the early days of the web, in 1994 and 1995, several people were working on enabling email to be accessed via a web browser. In Europe, there were three implementations, Søren Vejrum's "WWW Mail", Luca Manunza's "WebMail", and Remy Wetzels' "WebMail", whereas in the United States, Matt Mankins wrote "Webex". Three of these early applications were perl scripts that included the full source code available for download. Remy Wetzels' version was a CGI program written in C on Unix.
In 1994, Bill Fitler, while at Lotus cc:Mail in Mountain View, California, began working on an implementation of web-based email as a CGI program written in C on Windows NT, and demonstrated it publicly at Lotusphere on January 24, 1995.
Søren Vejrum's "WWW Mail" was written when he was studying and working at the Copenhagen Business School in Denmark, and was released on February 28, 1995. Luca Manunza's "WebMail" was written while he was working at CRS4 in Sardinia, with the first source release on March 30, 1995. Remy Wetzels' "WebMail" was written while he was studying at the Eindhoven University of Technology in the Netherlands for the DSE and was released early January, 1995. In the United States, Matt Mankins, under the supervision of Dr. Burt Rosenberg at the University of Miami, released his "Webex" application source code in a post to comp.mail.misc on August 8, 1995, although it had been in use as the primary email application at the School of Architecture where Mankins worked for some months prior.
Meanwhile, Bill Fitler's webmail implementation was further developed as a commercial product which Lotus announced and released in the fall of 1995 as cc:Mail for the World Wide Web 1.0, thereby providing an alternative means of accessing a cc:Mail message store (the usual means being a cc:Mail desktop application that operated either via dialup or within the confines of a local area network).
Early commercialization of webmail was also achieved when "Webex"—with no relation to the web conferencing company—began to be sold by Mankins' company, DotShop, Inc., at the end of 1995. Within DotShop, "Webex" changed its name to "EMUmail", which would be sold to companies like UPS and Rackspace until its sale to Accurev in 2001. EMUmail was one of the first applications to feature a free version that included embedded advertising as well as a licensed version that did not.
Hotmail and Four11's RocketMail both launched in 1996 as free services and immediately became very popular.
Widespread deployment
As the 1990s progressed, and into the 2000s, it became more common for the general public to have access to webmail because:
In some cases, webmail application software is developed in-house by the organizations running and managing the application, and in some cases it is obtained from software companies that develop and sell such applications, usually as part of an integrated mail server package (an early example being Netscape Messaging Server). The market for webmail application software has continued into the 2010s.
Rendering and compatibility
Email users may find the use of both a webmail client and a desktop client using the POP3 protocol presents some difficulties. For example, email messages that are downloaded by the desktop client and are removed from the server will no longer be available on the webmail client. The user is limited to previewing messages using the web client before they are downloaded by the desktop email client. However, one may choose to leave the emails on the server, in which case this problem does not occur. The use of both a webmail client and a desktop client using the IMAP4 protocol allows the contents of the mailbox to be consistently displayed in both the webmail and desktop clients and any action the user performs on messages in one interface will be reflected when email is accessed via the other interface. There are significant differences in rendering capabilities for many popular webmail services such as Gmail, Outlook.com and Yahoo! Mail. Due to the varying treatment of HTML tags, such as <style> and <head>, as well as CSS rendering inconsistencies, email marketing companies rely on older web development techniques to send cross-platform mail. This usually means a greater reliance on tables and inline stylesheets.
Privacy concerns
Although emails stored unencrypted on any service provider's servers can be read by that service provider, specific concerns have been raised regarding webmail services that automatically analyze the contents of users' emails for the purpose of targeted advertising. At least two such services, Gmail and Yahoo! Mail, give users the option to opt out of targeted advertising.
Webmail that is accessed over unsecured HTTP may be readable by a third party who has access to the data transmission, such as over an unsecured Wi-Fi connection. This may be avoided by connecting to the webmail service via HTTPS, which encrypts the connection. Gmail has supported HTTPS since launch and in 2014 began requiring it for all webmail connections. Yahoo! Mail added the option to connect over HTTPS in 2013 and made HTTPS required in 2014.