Recently an ex-colleague of mine was purchasing subscribers from a solo ad provider.
He wanted to duplicate his list i.e. copy it to another bulk email service, and when he asked his provider for advice, he says its against the TOS. He's only allowed to have these subscribers on 1 account, 1 list.
Long story short, he "threatened" him that he would find out if he did that because every list he helps build for people have some kind of bot or tracker that will notify him if someone tries to do things like that.
My question is... is he full of bull? or is there a tracker/bot that can do this ? The only way i can think of this happening is if he only subscribes to your list and doesn't subscribe anywhere else and suddenly starts receiving a 2nd email from somewhere else.