There is a form and people you can talk to if the form doesn't work. The form should have been mentioned in the reject message but is at <https://senders.yahooinc.com/contact#sender-support-request> though you should first review their information, rules, etc, starting at <https://senders.yahooinc.com/>, and the mailop mailing list at <https://list.mailop.org/listinfo/mailop> is where you can ask for help if the former doesn't suffice that will often result in direct contact with someone at Yahoo! that can get things done or at least give knowledgeable advice.