Great Circle Associates List-Managers
(December 1997)

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Subject: Re: Juno.COM
From: jtlist @ pigsfly . com (Jerry Trowbridge)
Organization: Flying Pig Ranch
Date: Fri, 12 Dec 1997 23:41:45 GMT
To: cnorman @ best . com
Cc: dattier @ miso . wwa . com, list-managers @ GreatCircle . COM, cnorman @ shell7 . ba . best . com
In-reply-to: <>
References: <>
Reply-to: jtlist @ pigsfly . com

On Fri, 12 Dec 1997 12:43:47 -0800 (PST), Cyndi Norman
<> wrote:

>Let me rephrase: what the heck is an "envelope recipent" ???  I'm guessing
>it means a group of people you are mailing to without actually specifing
>their addresses. 


When email is sent under SMTP, the headers aren't actually used during
the sending process. The sending computer, in the mail transfer
negotiation, sends a message to any number of "envelope addresses."

For instance, let's say that I send you a piece of mail, and send my
partner Ray a bcc:

The bcc is in the header when the mail leaves my mail client, but the
Mail Transfer Agent, sendmail for most unix machines, takes the
headers and processes them to see where to send the mail.

It takes all the addresses in the to: header, plus all the addresses
in the cc: header plus all the addresses in the bcc: header. It then
removes the bcc: header, adds any path header information it wants to,
and then organizes all the recipient addresses so that if more than
one person at the same domain is getting a copy, it only contacts that
domain once.

Let's say my partner ray is at a different domain than I am.
(remember, we sent him that bcc:) So my MTA (Mail Transfer Agent)
contacts his domain, and sends him a copy of my mail to you. At this
point, his name is nowhere on the "mail" per se. It only exists in the
"envelope" which is the pre-mail-transfer negotiation between the mail
clients that set up the SMTP session.

Unless the receiving machine adds his name in a path header: "received
[timestamp] by [hostname] as [messageid] for" his name
need not ever appear on the mail.

Take a look at a piece of spam (I'm sure you have one lying around),
and you'll see that the to: header is probably forged, as is the from:

The way the mail got to you was through the "envelope address" which
was given to your mail host when it received the mail on your behalf.

Jerry Trowbridge
--at the Flying Pig Ranch

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