Are you incentivizing or otherwise 'forcing' signups? Making users sign up to receive special content? Could be they signup on one of your campaigns, the cont

Are you incentivizing or otherwise 'forcing' signups? Making users sign up to receive special content? Could be they signup on one of your campaigns, the content doesn't meet their expectations or they become bored. Instead of unsubscribing they just click spam. Are you using double-opt in?