I have had this a few times now: go to delete a SPAM e-mail and I get a pop-up window saying that the sender wants a notification that the e-mail has been deleted or read, send yes/no.
I of course never send as all it would do is confirm my e-mail address as being valid.
What I was interested in letting people know is to check your default setting in your e-mail program to make sure it is not automatically sending such notices without your knowledge. Just another way to protect your e-mail address. I am sure I had to set this in Outlook as the default was to just send them.