AK you may want to try this:
Yahoo SpamGuard rates email for possible spam and sometimes incorrectly identifies something you want as spam. First, go to Options, Mail Options and then Spam. Make sure the email address you want is not in the Spam box or the Blocked address box. Even if the address is not there, you may have to click the Not Spam a few times for Yahoo to learn that this is a type of message that you want.