Oddpost was a pay-for webmail service, in 2002, that pioneered the use of JavaScript to mimic a desktop mail application, the first notable foray into using Ajax methodologies for webmail.  Ajax techniques minimized the amount of data sent during an email session by sending "Datapacks" instead of reloading the whole interface on every click like a traditional webmail service (Hotmail, AOL). This made the service much faster, at the time, than its counterparts.