Every email list is going to have subscribers who sign up and then apparently vanish. They may have opted in to a specific offer, then disengaged once they obtained the coupon, free content or other benefit you promised. Or they joined your list while in the market for your product or service but soon afterward their needs were met and they never bothered to unsubscribe. Inactive subscribers frustrate marketers because we don’t know what went wrong. Reasons they ignore us...