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 and Yahoo! Mail.VPractically every webmail provider offers email access using a webmail client, and many of them 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. ProtonMail, founded at the CERN research facility in 2013, is a Web-based email service which provides secure encryption.
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. There exist also other software tools to integrate parts of the webmail functionality into the OS (e.g. creating messages directly from third party applications via MAPI)