How or why is it possible to recieve someone’s email, that was not addressed to you? In another words the “To” field has an e-mail that is not yours, yet winds up in your In Box

I received an e-mail with an attachment( this case a resume) in which the receipiant's address appears at the top (normal) but it is not my e-mail address. Parts of the mail were blocked for safety reasons unless I accepted it (I did not) nor did I open the attachment. So why am I getting someone else's email?