I thought that CAN-SPAM blocked it, too, and it is often repeated. But CAN-SPAM prevents emailing someone who has opted-out, it doesn't require an opt-in. I talked to my HubSpot Success rep about this a month ago, because cold email is common practice in our industry and we are losing ground playing by rules others don't follow. Their terms are what prevent us from using HubSpot in this way, not CAN-SPAM. And on their side it has more to do with protecting their shared sending domains (unless you pay for a dedicated sending IP address).
We are still looking for another solution outside of HubSpot, but at a certain scale and market it might make sense to renegotiate terms instead.
