How do I know that colleges received my TOEFL score?

I sent the four free score reports that are offered while registering for the TOEFL. However, none of the colleges have confirmed that they have received my scores. Do colleges send a confirmation? If not, how can I be sure that they have received my scores?

If the colleges receive my TOEFL scores now and I don’t send TOEFL scores while applying, how will the colleges know that I have sent my scores earlier?

I’m curious as well.