I did send a request emails several times to Apple(default-mail-app-requests@apple.com) to register our email apps to get permission to use the default email client. But I didn't get any response from Apple. I don't understand why you don't reply to me or any guide to let me know what I should do more. I sent the emails by 9foldersinc@gmail.com because it's the email used when we registered our email apps in Appstore. Please let me know how to do for getting permission to use the default email app in our apps.