[Jimbuna]

Webmail (or web-based email) is any email client implemented as a web application accessed via a web browser. Examples of webmail providers include AOL Mail, Gmail, Outlook.com and Yahoo! Mail. Practically 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.

http://en.wikipedia.org/wiki/Webmail

I use Microsoft Outlook

Like most client programs, an email client is only active when a user runs it. The most common arrangement is for an email user (the client) to make an arrangement with a remote Mail Transfer Agent (MTA) server for the receipt and storage of the client's emails. The MTA, using a suitable mail delivery agent (MDA), adds email messages to a client's storage as they arrive. The remote mail storage is referred to as the user's mailbox.

Emails are stored in the user's mailbox on the remote server until the user's email client requests them to be downloaded to the user's computer, or can otherwise access the user's mailbox on the possibly remote server.

http://en.wikipedia.org/wiki/Email_client

My ISP 'Virgin Media' has this facility and I can access it from any computer.