Are you sure those email addresses are correct. I didn't know Verizon had any email service with or without Yahoo.
Yes, it's an old "grandfathered" email service that they no longer offer to new customers. Evidently, it's not very common.
I finally got an excellent VZW rep on the phone that investigated and figured out the situation for me. The problem was that the outgoing port should have been 25, not 587. Also, it's set up as a POP not an IMAP.