No.
Through the use of the email2 Web Client, there is nothing to install on each computer to get started using email2. For email2 power users, we do recommend installing the email2 Toolbar for Outlook (which does require something to be installed on each computer) in order to keep your staff's workflow the same as it is today (e.g. seamless use of basic email and email2 within the same email client).
// Edited July 2008