is it possible to trace an email from another country?

[Hilda]

Long story short,my sister met a guy on tagged.com
he says he is in Nigeria on buissness.
He gave her a sad story about his son being in hospital there and they won't let him leave country until hospital bill is paid. They will only take cash. They have taken his passport.
He doesn't have cash,doesn't have access to credit card.
TO ME it all is B.S.! She is gulliable and lonely.
I don't want her to be taken in on a scam.
So I had her send me one of his emails in hopes that I could trace his email addy.
Well the trace came back from Sunnyvale,Ca.
He has email through yahoo and that is where yahoo,corp is located.

What I need to know is how to find out for sure he is in Nigeria?

Thanks.