I sent an email to an incorrect email box.  Why dont I get a return email telling me that?

incorrect doesn't mean doesn't exist

Easy.  The email systems have no clue what your intended address was supposed to be.  So the systems assume that whatever address you use is the one you intended to use.  

Bottom line...you didn't get a return email telling you that you sent your email to the wrong address because it doesn't know that was the wrong address.

you won't get a failure email notice unless it's an invalid email. if the email address is valid, it goes through, even if it's the incorrect one.

There is no way to do that. Yahoo doesn't offer read receipts: https://help.yahoo.com/kb/sln3386.html

Because the computer doesn't know who you were trying to send it to.  It would have to be able to read your mind.  The whole point of email is that you can send mail to any valid address.  Some inboxes are set up to send automatic replies but the user of that inbox has to set it up that way.