Help with spam header

Howdy,

My wife has been getting 'delivery notification' failure messages from
spam - about one every other day. Can someone with more
header-detective skill tell me if:

1. We have a trojan sending spam (I think I ruled this out because the
IP in the original spam is not ours/RoadRunner?)

2. There really is a spammer using my wife address.

3. This is just spam

Thanks,
xnappo