Welcome to my world. I work on email deliverability for a financial services company, so no, I'm not a spammer. Hotmail makes two tools available to you to help you get your email delivered:
MSN Smart Network Data Services:
http://postmaster.msn.com/snds/ [msn.com]
This will let you put in your SMTP's IP address and it will give you consolidated stats on how much mail was received, and how much was filtered as spam.
Sender Score Certified:
http://www.senderscorecertified.com/ [senderscorecertified.com]
This company will "certify" you as a safe sender, and Hotmail will let your emails in unfiltered. The catch is you have to pay for this.
Good luck. It isn't easy, but at least there are some tools at your use.
