It would be ideal if you're a serious email user or you can become one. Whatever you do, dogfood it. Use it for your day to day email as much as possible as so

It would be ideal if you're a serious email user or you can become one. Whatever you do, dogfood it. Use it for your day to day email as much as possible as soon as the probability of it losing/corrupting messages is low. If you find yourself going back to your old client, write the code you need to so you don't have to. Decide what's going to be the most important things about your app and work hard to get those right. All the "it would be cool if.." stuff can wait till later. Only focus on the essence to begin with. Then, release it and see what people think and go from there.