Email Spam Being Sent From Phpmailer

We started having an issue with one of our sites that has CS-Cart installed where emails were being sent out from the main admin email and they were bouncing back as undeliverable. As the topic of the email it says, "Please confirm subscription" but we do not have the newsletter turned on. We also turned off the comments. I did notice that there are 268 "pending" subscribers to the newsletter but the only newsletter I have active is the one that links customers to my mailchimp account.

As this site is just an informational site I also noticed that on March 2nd an account was set up for.

...which is about the same time the emails for the newsletter get sent out.

So my question is, how do I turn off this part of the "newsletter" that appears to be the old one that sent the emails from the website and leave on the mailchimp newsletter addon.

Site is using CS 4.3.4.

After playing with this for a while I now see that the "Email Marketing" add on, which says it...
"Synchronizes your newsletter subscriber lists with MailChimp and Mad Mimi"

...actually puts the email right in the software. This is what has been sending out random spam request to people asking them to confirm the subscription that they never requested.

The email address that somehow set up itself as the only user on this site other than the admin is listed on multiple websites as a source for spam. My guess is this known spammer must have figured out how to get in to the CS-Cart system to send out spam garbage.

I have now disable the newsletter on that particular site but I did find the same spammer email user on another one of our sites using the same version of CS-Cart.

The spamming from the website has stopped since we turned off the CS-Cart newsletter. If you have the email address from... your system odds are something is trying to attack your system too. I am unsure if this is a hack or how this "user" accomplished this but it sure sounds like it/they are taking advantage of some type of vulnerability within CS-Cart.