I had eighteen emails in my inbox this morning, and sixteen of them were "legitimate" spam. By "legitimate" I mean each email was advertising a legitimate service, and their address, phone number, and valid email return address was included. Most of them come from businesses the company has ordered something from in the past, and the rest are probably harvesting the company "contact us" email address from legitimate sources or buying it from address list resellers. Of the sixteen emails, only two were anything I would have even the mildest interest in. Email is so cheap that there is little reason not to send out many thousands of solicitations. But there is a real cost, and it is shifted in email to the recipient.
But the lesson here is that I delete this ruthlessly, usually without even reading them. And some firms that I have ordered from and so see me or the company as a repeat customer are the worst. I don't want or need a "weekly specials" email, week after week, month after month. I unsubscribe from these lists, and some emails stop, but others pop up. And unfortunately, I don't see any solution to the problem.