SaaS
I've often made the point here that the advertising industry only sells advertising. "Do you want to show an advert to someone who's interested in buying buying a dishwasher? We know who's interested in buying dishwashers. [soto voce We know because most of them have just bought one.] Just give us your copy and lots of money and we'll make sure they see your copy every time they go online."
It's hard to believe that the customers, the advertisers, aren't kept in the dark as to just what they're getting for their money. The operators of this sort of scam don't need to confine it to the web. They can offer a spam as a service in the same way.
At the lower end of the market the delivery is to every address that's been scraped of Usenet or anywhere else more than a decade ago*. A lot of these offer some sort of business service such as SEO, website development or more recently mobile app development. The alleged senders have obviously been sold leads generation as a business opportunity, not realising they themselves were the actual business opportunity for whoever sold them the service.
To get into that sort of business you don't even need a great command of your email software. For instance I've had a string of spams all with "Re: " in front of the subject so it looks like one email being sent to a script that responds as a reply to a BCC list. However the first version had a bug: all the emails had the greeting "Hello wilfosula gmail,". Today, however, I find the script's been improved. It now has my name in there. However it's exactly the same text as the last of the wilfosula emails and what's more two arrived together but with different reply addresses.
They usually get a variation of my potential supplier questionnaire. That starts off by asking business-like questions they won't be able to answer such as their registered business name, domain name and, for SEO, their web address so that I can test their ability by finding them on the first page in Google when I Google for "First page in Google". It works round gradually to asking them if they think they can get their money back from whoever sold them this shit. Given the nature of today's pair I CCed the questionnaire to both of them.
* These emails all arrived at an address that I haven't used on Usenet for well over a decade but it's one I still use for some purposes. If a more recent Usenet address were to be used I'd set it to bounce with a "because of spam" message for a while & then just kill it.