Yeah, Like Nuk Said, check the header info.
It normally has routing info as well but you can normally find the originating IP fairly easily.
Where to find header info normally depends on the mail client you are using.
Or if you fancy doing it the other way around.
You can even get someones IP if they open an email you sent if you have a hotlinked unique image in a HTML email.
And you can normally pull a lot more info through log tracking that way.
This isnt really email spoofing though, email spoofing is sending an email and making it appear to come from another email address.
eg sending an email with a spoofer and make it appear to come from
bill@microsoft.com