Normally when you view an e-mail message in your inbox, it shows only the "From" address, the "To" address (typically your address, but also including anyone else the message was sent to), the "Subject" line, and the date sent. The "full headers" can show more information about where the message was sent from and what path it traveled before reaching your inbox.

Recent articles have explained how to view full headers in Hotmail, for example. Gmail, confusingly, doesn't make this option easy to find, but here's how to do it:

Start with an open e-mail message whose full headers you want to view. (Below is an example of spam that I received, so I'm curious to see where it came from. For privacy reasons, I've "scratched out" the addresses of the senders whose messages are in my inbox.)

In the upper right corner of the message, to the right of the word "Reply", is a box with a downward-pointing arrow. Click that box:

and click the "Show original" option:

This will open up a new window displaying the full headers of the e-mail message:

What the full headers mean, and how to read them, is a much longer and more complicated answer. This article just explains how to view full headers in Gmail, since Gmail makes it far from obvious where to find that option!

Simply close that window when done viewing full headers.

Bennett Haselton is a technology and political blogger who also runs a mailing list that lets you receive unblocked Glype proxies by e-mail.