You could just try Maildroid app. Its a free 3rd party app that I've found works best with Yahoo mail specifically. I receive my Yahoo emails almost instantly without dealing with polling issues like you do on K9 or HTC, and since my Yahoo mail is my main account, I tested everything for at least a month before I settled happily on Maildroid. No battery drain either. You could forward your mail to gmail like another guy suggested, but if you want to stay within yahoo mail and have access to all your folders, etc. and have a clean, fast app that handles Yahoo mail REALLY well, try it. Oh and the developer is THE most responsive and helpful developer who responds within HOURS, not days, to all email questions/requests. The app is always updating and improving and adding new features so if there's something you don't like or dont understand, email him and he'll help you. I ended up paying for the paid version (which is the same just with no ads) to support the dev but its your call. Since email is a HUGE part of my life, and yahoo mail had occasional issues for me when I first got my phone, Maildroid was what saved me so I've since been one to quickly prescribe it to solve most email issues that I see on these forums. I just bought my mom the Rezound which is why I'm here. It's a badass phone and hopefully this advice helps your situation. Good luck!