You can also set your email notifications on or off in the settings panel: http://hubski.com/pref?id=Isherwood
All those settings that end with "alert" are the toggle controls for your email notifications. Some people hate getting a pile of email and some love it, so it's up to you to decide what you want.
As elizabeth said, the color of the hubwheel next to your name changes when you have notifications. Since you are new and didn't know this, it has probably been orange most of the time. I always notice it though and obsess over reading, replying, and dismissing notfications whenever I get them.
Let us know if you have any other questions or anything. You can shout me or thenewgreen out anytime by wrapping our names in @ signs.