What are E-mail Headers?
There are two kinds of headers:
Partial (or basic) headers are the default display in most e-mail programs. The following are all included in partial e-mail headers: who the message is from, to whom the message was sent, a subject line indicating what the message was about, and the time-stamp of when the message was written. All of this information can be easily forged and rarely reveals the origin of the message. The practice of forging this information is know as spoofing, and is commonplace amongst SPAMmers.
Full (or extended) headers include more information about the message and how it got to you. Sometimes they contain the name of the user who sent the message. Even if the exact user can't be pinpointed, the user's network or Internet service provider will be revealed. This information is very difficult to falsify. Full headers are most helpful in forwarding junk messages to investigators.