Spam
I'm currently receiving a load of failed mail back to my domain from spammers. Obviously they have picked my domain to use as an address to spam from. There is nothing I can do about this.
I have tried to have a Sender Policy Framework line added to my DNS entry, but my hosting company (1&1), refuse to do it for shared hosting. Of course, there is no reason why they can't do this, apart from that they would make more money from me for my own server.
So, for anybody trying to find out where that spam came from, I'm terribly sorry, but my hosting company doesn't seem to be interested in stopping it.