I keep getting this message whenever I send a friend an email - "Remote host said: 550 relaying denied for" then it lists his email. What is this. Has my friend blocked me. How can I tell if someone has blocked me. How do I know if it is a problem with Yahoo?
In general, I'm not sure how you can tell if someone has blocked you; however, the 550 error is a current problem with Yahoo. It's extremely frustrating, and they seem to be in no hurry to repair it. Grr.
Does this happen when sending from mail.yahoo.com? It sounds like you are using a POP mail program (Outlook, Thunderbird, Mac Mail, Windows Mail, Entourage, et cetera), and if so, which ISP do you use? If it's Comcast, Comcast is blocking it. Call Comcast and they will explain you must use Comcast's SMTP servers to send mail.