Contact form to send to hotmail support about your email bounces (from outlook.com, MSN, etc..

I am not sure if you get any information back about the infraction but it  is worth a go. The following might also be true.

Hotmail, which is operated under Outlook.com now, is provided by Microsoft. You can request they remove your IP address by completing the form here (this may require signing up for Outlook.com first).

It will take a few days for them to investigate the report, and if your IP address was not associated with sending Spam, you'll receive an email back from their support team. It will then take another 24-48 hours for the IP address to be fully unblocked in their system.