This has nothing to do with your N900. Your Hotmail account has been hacked. This happened with many Yahoo Mail accounts. Passwords over a certain age weren't secure. I believe you could even have changed the password back to THE SAME PASSWORD and that would have still solved the problem because it was the obsolete way the password was kept thay allowed a spammer to trigger a message being sent to your contacts. I am not an expert, and the above is an approximation of the story as I understand it.