I keep recieving "Delivery Status Notification (Failure)" messages every 10 minutes in my inbox. The content of the messages being sent from my servers is clearly spam. I have not sent any messages, nor given permission for anyone else to do so. I think someone has exploited some web application on my site and is using to send mass spam emails. The delivery notification failures I am getting is because some of the emails that are being sent are being rejected, and I am getting them.
I am running PHPlist, PHPadsnew, and phpBB. I have changed all my passwords. I have removed PHPlist because I was not using it. I just updated PHPadsnew to the latest version, and phpBB is up-to-date as well. I'll wait it out and see if I get anything more.
Is it possible that someone is using a script on my site to send mass spam emails? Or could it be my host's fault (because the site is hosted on shared hosting)?
I have sent and email out to my host as well notifying them of the problem, so they don't blame me for the spam. Yikes!
Is there anything else I should do? Anything I'm forgetting? Thanks.