Consent.

How can you consent to learn about something you don't know about? This is a very different idea to me and I'm trying to understand where you're coming from.

IMO, if i did not sign up for information regarding a product, its spam. If i want something, i will go look for it. I don't want random strangers trying to sell me something, especially when they have no idea what i need.

What if the random stranger is telling you about something you do want, but didn't know you wanted?

If the address on an email list was obtained via some other party that the address was voluntarily submitted to (say, a service with a ToS that included sharing your email address with "partners"), then consent was already established. Doesn't mean it isn't still shady.

Unless it was specified for what purpose the email was obtained, consent isn't established.