In an email the body (content text) is always preceded by header lines that identify particular information of the message, including the sender, recipient, date and the subject. Some headers are mandatory, such as the FROM, TO and DATE headers. Others are optional, but very commonly used, such as SUBJECT and CC.
You can use email headers to trace where the email came from, including how it got from the sender to the recipient's mail servers.
Find your email headers
Email clients are all different, so you'll want to check out their help pages. Choose your email client or application to find out how to locate your headers.
Locate the full email source
The steps to locate the full source of your email are totally different for all the email clients. Search on the web for your email client or program in order to get the specific instructions needed to view the email's source, or check out SpamCop's resources.