While there might be indications and pointers in the email and logs if the offender wasn't careful, email as is doesn't provide any ways of mapping mails to locations.
Content of the mail, including all headers, is totally up to the sender. Thus, you can't trust any info that you extract from the mail itself. I'd call it easy to forge, if there was even the slightest hurdle.
You can look into your server's logs to figure out which host forwarded that mail to you. Usually, that wouldn't make you any smarter - either it's not some large anonymous mail provider abroad, or someone else's mail server, and the account on that used to send the mail might just as well be stolen.