Most likely, someone is using your e-mail address as a "spoof", so that it looks like you have sent the e-mail, then it tries spamming all these invalid addresses and you are the lucky recipient of all the "delivery failure" messages. It happened to me and for about a month, I got on average about 200 "delivery failure" messages per day. My ISP
could care less, so I was tempted to just let them fill up my mailbox (I quit using the ISP
required e-mail account anyway), but then I figured they'd punish me, so I dutifully checked the e-mail and promptly deleted everything.