If I am innocent, I will tell the ISP that fist.last@example.com opted in, and I will be telling the truth. If I am a spammer, I will say the same, and I will b

If I am innocent, I will tell the ISP that fist.last@example.com opted in, and I will be telling the truth. If I am a spammer, I will say the same, and I will be lying. So what difference does it make?