Earlier quoted context omitted.
A 4% signup rate actually signifies really well targeted emails. Not everyone who doesn't sign up is annoyed by the mail (or did even open or read it). I think this is far from beeing spam, where you would see signup rates well below 1%.
SPAM is any unwanted email, phone call, SMS, or other form of contact. SPAM is defined by the recipient, not the sender. Thus, if you're trying to justify something as "not spam" by saying it meets or doesn't meet some criteria, then it's probably SPAM.
Sounds like advertising. I don't want any ads in my imgur feed. I don't want any ads in the magazines I _BUY_ I don't want any ads in the movies I PAY to go to watch (trailers and "buy candy and popcorn clips").
If an email is an email about a thing or service which is related to my interests, but I don't recognize the company, I suppose that falls under spam, but that's better than random emails for prescriptions or scams.