I am getting this email after upload my binary with Xcode Version 6.0.1 (6A317)
Your binary is not optimized for iPhone 5 - - New iPhone apps and app
I got the same error, but in my case I didn't had the storyboard (xib) file for the launch image, which is needed:
"You use a launch XIB or storyboard file to indicate that your app runs on iPhone 6 Plus or iPhone 6." (see here)
I followed this tutorial to create it: https://developer.xamarin.com/recipes/ios/general/templates/launchscreen-xib/
For step 9 of the turorial, in the Info.plist, I set:
UILaunchImageFile~iphone
Launch Screen.storyboard
Just to verify, when you run your app, you should see your launch screen image before it loads. After I did this, I was able to upload the app to the app store.
Steps showed above in other answers are also important: "If you also need to support earlier versions of iOS, you can continue to supply static launch images in addition to a launch file." (see here)
Hope this helps.