Do spammers pay any attention to "Delivery Status Notification (Failure)" messages?
In most cases, no. They simply obtain a list of emails and use some mass emailing software to blast out to all emails in the list, irrespective of whether they get any delivery failure/bounce reports or not. Its simply not worth the time to clean their lists..
I have tried the following tactics and it still seems spam gets through:
1. individually going through every email and unsubscribe - very time consuming
2. just deleting the email without reading it
3. in some cases - just labeling it as spam