Returned Mailer Issues

I am having a lot of people saying that they are getting returned mail's from messages they never sent. What could be causing this. Like the mails appear to becoming from my host but they said they never sent to these people, but the wierd thing is it all seemed to start happening when I found out I was on the backscatter hotlist. Which, I applied the fix you mentioned. So am I not sure where to go from here.

Status: 
Closed (fixed)