Hi Andrew,
Thank you for contacting Yahoo Mail.
Based on the information we've gathered, we're unable to offer prioritized delivery privileges to your sending IP(s) at this time. We can't provide you with specific information other than to encourage you to evaluate your mailing policies and practices to see how you may be able to improve your sending reputation. We encourage you to review some of our recommended best practices for sending to Yahoo Mail.
Another option is to register for the Complaint Feedback Loop program.
Yahoo Mail offers a free Complaint Feedback Loop program to help email senders minimize complaint rates. If you participate, Yahoo Mail forwards complaints from our users about emails sent from your organization.
Your patience is greatly appreciated.
Regards,
Frank
Yahoo Customer Care
http://help.yahoo.com