If they are delivery failure notices from messages that you didn't send, then more than likely some spammer semi-randomly picked your reply address for his from: in a spam run.
(Even more likely if you have your own domain)
It's happened to me a number of years ago, and has happened to some friends of me as well. Since SMTP does NOT verify the address listed as FROM: yet the receiving servers do use this to send delivery failures to, there is absolutely nothing you can do to stop this.
Anyone with half a clue can tell by looking at the headers that you aren't the real sender though, so you probably won't get into problems with your ISP over this.
As far as finding the real sender: the only thing you can find out is the IP address of the real sender. based on that you can find out his/her ISP (through ARIN.net of APNIC.net), who in turn should be able to match the date/time + IP to one of their user connections... But the sending ISP is the only one who can find out the true sender, you can't do that on your own.
On the bright side, it rarely lasts longer than a week, spammers switch sending addresses/domains frequently. :-/
(Even more likely if you have your own domain)
It's happened to me a number of years ago, and has happened to some friends of me as well. Since SMTP does NOT verify the address listed as FROM: yet the receiving servers do use this to send delivery failures to, there is absolutely nothing you can do to stop this.
Anyone with half a clue can tell by looking at the headers that you aren't the real sender though, so you probably won't get into problems with your ISP over this.
As far as finding the real sender: the only thing you can find out is the IP address of the real sender. based on that you can find out his/her ISP (through ARIN.net of APNIC.net), who in turn should be able to match the date/time + IP to one of their user connections... But the sending ISP is the only one who can find out the true sender, you can't do that on your own.
On the bright side, it rarely lasts longer than a week, spammers switch sending addresses/domains frequently. :-/