For one, I don't know of any client that still loads remote images without confirmation, much less 1x1 tracking images. Secondly, if I can sign someone else up

For one, I don't know of any client that still loads remote images without confirmation, much less 1x1 tracking images. Secondly, if I can sign someone else up without their knowledge and get you to send then unsolicited mail, you're risking legal problems.