The E-mail button is located in the command bar and is disabled by default on IE9. The command bar includes the following buttons -> Home, Read mail, Print, RSS, Page, Safety, Tools and Help. You can enable the command bar by pressing the ALT button then View -> Toolbars -> Command Bar.
The email action is also available as a browser accelerator, and is visible when you right click on a web page. The default option is Email with Windows Live, but similar options may be available from other websites.