Why am I not getting my emails from ON-Star?

I had been receiving my car reports from On-Starr Co. (from General Motors) for the past few years. Now they are still being sent but not received either in my email or spam. We have checked all email addresses, and confirmed today that they again have sent two updates to my email address. They have verified that it left their system but Yahoo is not accepting it. Why??? I need these reports. Do I switch from Yahoo to another site.????