Microsoft provides a fantastic amount of data through their SNDS program (Smart Network Data Services) that can help marketers responsibly monitor their sending reputation to Hotmail / Outlook.com email addresses. That should include just about everyone sending email. The data is free and any sender that uses a dedicated IP can sign up at:
Performance and Enterprise Mail Monitor accounts now include the ability to automate and collect that data for review. All that is required is to have an SNDS account set up that is already tracking IP data. The Reputation tab of qualified Mail Monitor accounts walk you through the rest. This is a great tool for troubleshooting and monitoring delivery to Outlook.com and Hotmail.