I would like to send an email with a special app (Gmail or Email). How must this call be programmed (StartActivity (FinalEmailIntent)) to specifically call the respective app without asking?
StartActivity? That is as far as I know related to B4A. Are you sure you did post your question in the right forum? This is about B4J. Once this is sorted out it will be easier to help you. Erel can help you move your question in case it concerns B4A. For B4J you can use a backend service like PHP on serverside to perform this, and use OkHTTP library or later to communicate with the script. I hope this solves your problem.
B4A in general relys on the operating system which means that system calls is non-functions with B4J (Basic4Java) and system specific. B4J works differently and relys on the JavaFX framework. If I understand your question correct you want to access email from inside B4A (android mobile app)? As far as I know it's the messenging intent. Please post such questions in the Android forum B4A and not B4J since this is related to crossplatform PC and Macintosh (JavaFX) and not mobile devices (Android) in general.