Outlook has a list of unique keyboard shortcuts just like the other Microsoft Office apps. They cut down the time taken to move your mouse around and going through the menus. These shortcuts are the most commonly used features.
Ctrl+R: reply to email
Alt+R: reply to all in email or switch to the work week calendar view
Alt+W: forward email or switch to the weekly calendar view
Ctrl+M: F9 to Send/Receive all
Alt+S: Send email
Ctrl+G: open the "Go to date" dialog to jump to any date in the calendar