Google is replacing its email app with Gmail 5.0 app on android lollipop (Android 5.0). The Gmail 5.0 was designed while keeping the guidelines of material design in the mind. This reflects that Google is giving much more importance on Material design in the forthcoming apps and OS updates. But there is no absolute opinion about this app, whether it is Good or bad. All the opinion about this app differs from person to person. But one thing is clear Google has made an immense effort to retire the Email application which was published earlier this year in the Play Store.
Gmail 5.0 can also handle your Yahoo accounts and Outlook in addition to Gmail accounts. So you can use one app to manage all your emails. So there will be not be need to install a 3rd party app to manage emails. Gmail 5.0 app update is expected to rollout shortly. So wait for your update.