For the last 4 days I haven't been able to read my email from my POP client or from yahoo. My email client says inbound.att.net rejected the password. I have not changed any settings for my email client.Is this a system wide problem?
I doubt there is a system wide problem. Have you tried contacting their support to reset your password?
Log into mail.yahoo.com with the full email and password. This does two things: 1, it makes sure the password is correct. 2, it clears the pop lock Yahoo will put on it for too many failed logins.