[NTLUG:Discuss] OT:E-mail Header How-To

[Jack Snodgrass]

The first thing to know is that the SMTP Protocol says that email is free 
form text. 
There is nothing that prevents someone from monkeying with the headers 
in an email. i.e. just because you have an email that says it is from 
god at heaven.org 
and heaven.org <http://heaven.org> has a valid ip address, it doesn't mean 
that the message came from god. 

The from: to: subject: date: etc headers that you normally see are all 
optional. You 
can compose an email and put those in or leave them out or do what ever you 
want 
with them. Some mailers will fill in any of the major ( subject, date, from 
) ones if you 
leave them out. Anything that starts with X- is just an 'extra' one that 
some mailer 
added... again... these are optional and you never know when it was added. 
It could 
be added by the original mail client, or by ANY of the mail servers that 
touch it. 

Speaking of mail servers, each mail server that processes the message is 
supposed
to put a received header with it's own info. You have no way of knowing the 
the mail 
server added the correct info, preteneded to be someone else, or removed 
headers. 

In generall... if no one is screwing with the email headers, the first 
received header
you see is the one that touched the message first. Then each other machine 
that 
touches it will add it's header to the top. The last one there should be 
from the mail 
server you recieved the message from. 

Does that help. ;) 

jack 


On 5/3/05, D <dmyhand at cox-internet.com> wrote:
> 
> Can someone recommend a good, concise explanation of how to read and
> understand e-mail headers? Thanks, Dennis
> 
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