Do not understand how the Mail program works

As I mentioned I would prefer that when a user tries to email some program data they get a choice as to which email app to use. I don't want to send emails without their explicit say-so. The Mail app is rather opaque. I sent about 10 emails last night evening and it took about 3 hours for the emails to actually be sent (from my machine to my machine). I was so used to what the Android does, immediately offer you the choice of what to do, that I was very surprised at what Windows does. And Microsoft being Microsoft (and sort of acting like Obama-obsessed trump) does not offer gmail as a default way to handle emails (AFAIK). You can choose Chrome but then...Chrome what? I was hoping for some industry-standing method of doing this, rather than rolling my own.