Regardless of how you name it.
Spam is SPAM
Under todays laws, maybe!
For your "marketing Materials"
You could export your database (and delete customers as
required ) to a specialised email external mailer program.
If you have a large number of customers you would want to "throttle" the number of emails sent so you don't overload ther server.
I don't believe what you want to do can be done without altering zen-cart core code.





