https://en.m.wikipedia.org/wiki/Feedback_loop_(email)
Further, pixels can be embedded in the email so they can see when you open the email and how many times.
The sender has every incentive to properly handle unsubscribe to avoid spam traps. If you get big enough, users WILL come sign up for your service with a known spam trap email. If your operations are as sloppy as you’re suggesting, your email sending capabilities go poof.
I think this risk is overstated. Individual spam recipients in the United States have no standing to sue under CAN-SPAM; only the FTC does, and there's a high bar to get their attention.
my university spams me. i bought a torch from olight. they spam me. i get food deliveries. they spam me. i bought some tech. they spam me. i look for real estate they spam me. i get a delivery. they spam me.
it's differentiating between the two that's unrealistic.