Re: No return
they just need to include a note:
"Peace and Prosperity to you and all your fellow Centaurian beings. I am Mr Amatee Mbogo, Finance Minister for a small nation-state on planet Sol 3 (which we call Earth) and am in possession of 274 bazillion Centaurian dollars. Please send a small finder's fee of 500 Centaurian dollars to the following space-time coordinates and a generous share of the fortune will be sent straight away."