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[Larry Stone]

On 3/8/05 8:45 PM, David Gibbs at david at midrange.com wrote:

> Sorry if this is a dumb question ... but what header indicates the
> "envelope sender"?

None. The "envelope sender" is the return address (MAIL FROM: command) in
the dialogue between the upstream mail server and your mail server. Then,
think of your mail server as being a very efficient clerk. It receives the
mail, opens the envelope, puts what's in the envelope in your inbox, and
throws away the envelope. Unfortunately by doing so, the envelope is no
longer available to see. Just as the From: header in a message can be easily
forged, so can the Envelope Sender.

Some (but not all) mail servers will added a pseudo-header before the real
header that shows the envelope sender or an additional header with it. I run
Postfix and I see it adds both the pseudo-header first (a From line with no
colon after From) plus a Return-Path: header which also has the envelope
sender in it. Looking at my mailman archives, the pseudo-From is there but
not the Return-Path: header.

-- Larry Stone
   larry at stonejongleux.com
   http://www.stonejongleux.com/