I sent two emails, both exactly the same, one after the other, and the confirmation came almost instantly.
But to be honest, not receiving a confirmation email shouldn't be a reason to worry, as long as you sent all the documents and you have proof of that, you should be fine.
I'm going to send one extra document tomorrow, I will send it twice. I'll probably won't get a confirmation email this time, but as long as we send everything before the August 4th deadline, we should be︀ fine.