Why am I getting mail delivery failure notifications for email that I didn’t send?
If you have received Mail Delivery Failure notices to your NetZero account for messages you have not sent, it is possible that the original spam message has your NetZero account name forged in the From field and/or the Return-Path fields.
Please note that spammers often forge innocent domain names (in this case NetZero) into the message headers in order to disguise the actual origin while creating confusion for Spam recipients.
Please forward the entire Mail failure notice (also include the original message that caused it) along with its full headers to firstname.lastname@example.org. so we may investigate the matter further.