Email push notification

I have been facing a problem in my yahoo email push notifications since I upgraded my iphone4 with iOS5. I mentioned this earlier in this forum to see if apple can release a patch to fix this but iOS 5.1 has the same problem. It will give me a notification if I hard reset my iphone everyday which is annoying. iOS4 used to give me an immediate email notification upon receiving a new email in inbox (when push were set for manual) but iOS5 is not capable of doing that unless I open my yahoo email or hard reset everyday.