But the person who sent the mail doesn't know where it ends up. These services are exactly like what the parent was talking about -- someone sends a letter to a

But the person who sent the mail doesn't know where it ends up. These services are exactly like what the parent was talking about -- someone sends a letter to a virtual address at the mail aggregator service, and the service then sends the letter on to your physical address. A 302 is like a letter that's been marked return to sender with a forwarding address. The original sender would then know the actual physical address.