Hi dlkimbro,
I'm sorry that you're not receiving from a specific sender. You may consider reporting the issue to Yahoo's support team so they look into any issues with the domain or filters. I apologize for the trouble.
I originally reported the problem to tech support and was assured it wasn't Yahoo but the rep claimed he reported it. The rep was self-assured and, at best, smug. It hasn't been solved, Social Security Admin flatly blames Yahoo and I think they're right. Shameful for all the finger pointing and lack of quality tech support.
