MAILER-DAEMON@yahoo.com <MAILER-DAEMON@yahoo.com>?

Somewhere in the Mailer-Daemon message it should say the reason the email couldn't be delivered. Double-check the email address you used (check for a space at the beginning or end. you can't see that). The most common reason would be an incorrect email address. Another reason could be a full In Box. Make sure the email address containing an @ symbol, and isn't a web address instead of an email address. Believe it or not, that's a common mistake.