Call function on email

I would like to call a serverless function when an email is received on certain email address (and then send a reply or trigger something else).

So far I found these two examples:

What I am wondering though:

  1. Doesn’t that mean that the mail for the whole domain (not just the one address) is getting processed by the function?
  2. Does Google (and maybe even Azure) have similar services to accomplish the same?