I'm not able to send email from Yahoo. It shows me message as user name or password does not match

Hello,

Yahoo has been configured on my iPhone. I'm able to receive email but while sending the email it gives popup as username or password does not match.

It gives two options as OK and Setting. Once you click on Setting it takes to Account and in that outgoing mail server is mentioned as Yahoo! SMTP. still outgoing of email does not work.