On Saturday 13 December 2003 04:09 pm, Greg Connor wrote:
--marrandy <marrandy(_at_)chaossolutions(_dot_)org> wrote:
spf is checking the :-
MAIL FROM:<owner-spf-discuss(_at_)v2(_dot_)listbox(_dot_)com>
by stripping the left parts away leaving listbox.com, looking it up in
DNS (with the rule you are using, a, mx, ptr or whatever, and comparing
it against the IP 207.8.214.5
A good explanation of the SMTP transaction.
A minor correction, in this example we would check SPF records for
"v2.listbox.com" first. The answer is "v=spf1 redirect=listbox.com".
Normally if there is no redirect you would not walk up the chain, I don't
think.
Yes sorry, I was tired.
In my experience, the Envelope address (meaning what the MTA said in the
MAIL FROM: part of the transaction) is usually recorded as "Return-Path"...
Yes, I said that in the first mail. That appeared a long time later. I
think the follow-up with additional info may have confused matters, but...
"The point to remember, is, that the MTA (mail server) that is processing the
message, will change the return path to it's name, when it connects to the
next MTA, it will say :-
MAIL FROM: <with it's return path name> NOT your original MUA (email
address) name.
It's late and I'm tired. If it's still unclear, I will try again once i get
some weekend choirs completed.
MAIL FROM: (return path - MTA) - May or may NOT be the same as the FROM: in
your MUA"
I believe that is why Return-Path is shown at the TOP of the headers; it is
added last, by the last MTA to receive it, based on what the other MTA told
it. Return-Path may or may not appear in your mail program, but if it does
that is a good indication that it was in the transaction outside of the
DATA.
Yes.
The DATA includes all the headers and all the body, but the MAIL
FROM command is seen by the server before receiving any headers.
Very close.
*Often* the "Sender:" header is the same as the Mail From
command/transaction and return-path, but sometimes "Sender:" is not shown
at all. There is NO rule that says the From: address in the header has to
match the Mail From command, and in the case of mailing lists it definitely
won't, since you want bounces to go back to the list server, and not each
sender, which might be different from where replies might go.
You had better be real careful here. This is how people get confused.
From: is what you see in you MUA
MAIL FROM: is a part of the SMTP transaction between Two MTA's and is added as
another header return-path:
Also, sender isn't required (many lists and MTA's don't add it) whereas
return-path: is required.
To emphasize what Martin and others have said... It is pretty common to
have 4 servers handling your mail. If the sender sends it to an
intermediate server that is not really the "outgoing" server, that's 2 on
the sender side. If the To: address domain has an "edge" server and a
"user mailbox" server, then that's 2 on the receiver side.
To clarify that, large organizations may have an :-
1) inbound (receive MTA requiring DNS lookups, virus checking)
2) inbound (receives mail from 1) then spam filters
3) A dedicated list server
4) an outbound (sending) MTA.
The point is, each inbound server, and each outbound server, is going to add
extra headers for tracking pruposes.
I'm choping the rest as it's getting long
--
Greg Connor <gconnor(_at_)nekodojo(_dot_)org>
Good follow-up Greg.
Regards...Martin
--
semper en excretus
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