Have you looked at the settings on your Hotmail account, specifically the ones related to publishing your info? You can choose to have your info included in the Hotmail public directory, which would make it easier for a spammer to collect your address.
I have had my account for a few years now, and only get a dozen spam messages a day at the most. As I use it as a garbage account when signing into websites, I am surprised I don't get more.
goates