I'm just trying to understand the rules regarding moon shots. I read up on them in the forums and it seems to be a simple arrangement based on trust between two players. I made arrangements with another player to trade moon shots. I sent an attack fleet to his intended planet and carried out the attack. He didn't send a fleet to me and is now ignoring my private messages. What can I do about this?

Attack him and destroy him. He has broken your trust and isn't going to listen to you. Claim vengeance. If he recycled your fleet, that's also milking I think. It's either milking, pulling, or pushing...I can't tell em apart, I just know if he recycled your fleet is against the rules.

You got ripped off. Destroy him like hime said

post his name after you destroy him so some of the rest of us can give him special attention

I love special attention .(even though I m a scavenger of debris).

you should probably wait just a bit before you hit him, he might have just not been able to get to his computer, judging by the fact that he's not answering messages, but if you're reasonably sure he ripped you off, go for it.