mail header, or http header, or ftp header, is those thing the server sending to each other, telling each other, what kind of information they both receiving
like,
who it is from, what type of text encoding, how the connection be handled after everything are done
etc
these header wont be seen in header, and human eyes
just the server will see it, and process it by the meaning of the sender
like http header
http 1.1 200 OK
content-type: text/html
connection: close
the above 3 lines are the most common type of header when u use browser (100% of browser will send this out)
do u see these 3 lines?
NO
so, the header in mail is same, it wont be seen by human eye, except the following
From:
(maybe more)
according to this link,
the For header isnt used like the way u do
http://www.avolio.com/columns/E-mailheaders.html