If I read you right,are you asking if a company send (say) an email to me and I don't reply,is there any way of someone (not in the company I assume) finding out the address is was sent to?
That depends on whether the sent email (copy in the PC that sent it)had been deleted or not.
Why do you want/need to know the address it was sent to?
This is one of the reasons that you should never reply/unsubscribe from spam.Once you do so the company knows that you have a "live" address and will continue to pester you.
I am sorry if I have not answered you,but your question is not that clear.