Simple answer to your query Jon is no, it isn't.
Spoof is the clue here; someone has sent an e-mail to your address that purports to come from a registered ISP that isn't supported by the IP address attached to it.
Just to be on the safe side, run a scan with your AV and ASW applications in safe mode to ascertain whether you have infected files or not.
If there are some dud ones, your apps. should deal with them; however it would be far better to keep your inbox clear on a daily basis than to have to rely on automatic software to do it for you.