You should stop using yahoo mail as your mail provider. Multiple times now Fedora has gotten flagged as a bad or spam domain because of a user action. I don't think these are intentional DOS's but the workflow is this:
1. Sign up for a mailing list or news letter. 2. Flag news letter as spam 3. Yahoo blocks the DOMAIN so now no yahoo users get mail from that domain.
If fedoraproject mail is important to you, use another mail provider.
