Yahoo mail is working fine on my Evo via k9 this morning. It could have been a temporary issue or account related. If it's not working now, try clearing out the trash and old email. If you have the Yahoo client on your phone, make sure you can access the account. As a last ditch effort, you could always re install k9 or give another client a try. It's also been my experience that Yahoo email works on 2nd party clients for a while till Yahoo changes something and it doesn't and it can work for one person and not another. Yahoo considers this access to be a plus service that you should be paying them for, so don't expect any support from them. Good luck!