Matthew Thomas on web-based email interfaces. Mail Models, part 1:

The scenario: A customer calls you to his computer, complaining that the e-mail message he was writing wouldn’t send, and now it has disappeared. He is unable to explain the problem in greater detail.

Mail Models, part 2:

The underlying design flaw here is the existence of Webmail, trying to put a usable e-mail interface inside a Web browser window.

Webmail and other “Web applications” will always be very difficult to use, relative to native equivalents — because they appear inside a browser window (causing absurdities such as scrolling “Send” buttons), because constant server round-trips to update the UI make them them disgustingly slow and flickery, and because they rely on a platform-independent interface abstraction (HTML forms). Webmail is only as popular as it is (and, indirectly, keeps me employed) because there isn’t a less execrable alternative which provides the same roaming ability.