What is Webmail?
In the early days of the web, in 1994 and 1995, several people were working on enabling email to be accessed on a web browser. In Europe, Soren Vejrum and Luca Manunza released their "WWW Mail" and "WebMail" applications, whereas in the United States, Matt Mankins wrote "Webex". Each of these early applications were perl scripts that included the full source code available for download. Also 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 in January 1995. Soren 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 Manuza's WebMail was written while he was working at CRS4, in Sardinia, with the first source release on March 30, 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 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. As Hotmail developed a foothold on the Free-email address market, EMUmail started MollyMail, a service to let you check your existing email from the web. After the Accurev acquisition the EMUmail webmail line was killed in favor of the SMTP.com email delivery service which is still sold today.
Rendering and compatibility
Email users may find the use of both a webmail client and a desktop client using the POP3 protocol a bit incompatible: 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 use of a webmail client in this mode is limited to previewing messages using a web client before they are downloaded by the desktop email client. On the other hand, the use of both a webmail client and a desktop client using the IMAP4 protocol has no such incompatibility: the contents of the mailbox will be consistently displayed in both the webmail and the desktop email client and any action the user performs on messages in one interface would be reflected when email is accessed using the other interface. There are significant differences in rendering capabilities for many popular webmail services such as Yahoo! Mail, Gmail, and Windows Live Hotmail. Due to the various 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.
Although every email service provider can read the email unless encrypted since it is stored on their servers, concerns have been raised about webmail specifically. Most popular webmail services tend to use what's called targeting ads and online spam-filter(instead of a client-based), these services searches through email for certain target words and even if the service providers claim that no humans reads the emails some of them have been forced to make it possible to opt this feature out. Because web browser is the expected way of viewing the inbox webmail providers store emails longer than usual providers which often delete the email from their servers after they have sent it to the email client.
Another concern is considering the fact that most webmail service providers are US-based and therefore are subject to the Patriot Act which means that US authorities can demand the company to handover what information they have about a user, without necessarily letting the user know, no matter what citizenship you have or where the information is stored.