ACTION_SENDTO only has the 'data' argument #3
Description
The documentation for Intent.ACTION_SENDTO doesn't list any supported extras.
EXTRA_EMAIL, EXTRA_CC, etc are only valid for ACTION_SEND and ACTION_SEND_MULTIPLE even though some apps also support them with ACTION_SENDTO. Receiving apps that only implement what is documented won't read the extras.
The documentation also doesn't mention a type for ACTION_SENDTO intents. While it is unlikely that setting the type to message/rfc822 is causing any problems today it might in the future.