Re: Email tutorial?
On Thu 26 Apr 2018 at 08:41:17 (-0400), Greg Wooledge wrote:
> On Thu, Apr 26, 2018 at 02:11:44PM +0200, tomas@tuxteam.de wrote:
> > That's right, mbox uses this one as marker. That's why a "naked" From at
> > the beginning of a line, like this one:
> >
> > From there and where
> >
> > gets "escaped" by prepending something (I think this is done by the
> > mail delivery agent).
>
> > I'm here "on" mbox, but I'd expect to have this line also in other
> > civilised mail storages (perhaps excluding Exchange/Outlook, but hey
> > do they count as civilised?)
>
> This piece of information (to whom errors should be sent) is called
> the "envelope sender". It's part of the SMTP conversation between the
> sending MTA and the receiving MTA.
>
> In mbox formats, the "From " header line may include the envelope sender,
> but I don't think it's guaranteed.
> <http://jdebp.eu./FGA/mail-mbox-formats.html> describes it as a
> "convention".
>
> In other formats, there is no "From " line, because messages are
> separated in a different way. E.g. Maildir stores one message per file,
> and MMDF uses 4 consecutive Ctrl-A characters within a single file --
> see <http://www.tin.org/bin/man.cgi?section=5&topic=mmdf>.
>
> Which is NOT to say that there is no record of the envelope sender in
> these other systems. In qmail's Maildir, for example, the envelope
> sender is written in a "Return-Path:" header line (by qmail-local --
> see <http://www.qmail.org/man/man8/qmail-local.html>).
>
> For other mail systems and mailbox formats, I would suggest consulting
> your documentation. Some may not store it at all. Some may copy
> Maildir's conventions. Who knows what the others do....
Yes, I was trying to avoid discussing the "From " line as this is
entirely dependent on the way mail is stored at your end. The
distinction is easy to see here: my emails originally sit on an IMAP
server; when mutt reads one, it's cached by mutt, and the first line
is:
Return-Path: <bounce-debian-user=deblis=lionunicorn.co.uk@lists.debian.org>
but when I save it (mbox storage), it starts:
From bounce-debian-user=deblis=lionunicorn.co.uk@lists.debian.org Thu Apr 26 07:41:56 2018
Return-Path: <bounce-debian-user=deblis=lionunicorn.co.uk@lists.debian.org>
where the timestamp is the last "Received:" time translated into
(but not marked as) local time. Mutt also adds the notorious
extra headers like Status:, Content-Length: and Lines:.
Anything above the first "Received:" line (obviously excepting "From ")
should have been placed there by my email hosting provider.
In my case, tomás's Envelope-to: becomes a paired X-Original-To:
and Delivered-To: (but no Delivery-date: as they don't use exim).
Information about the original email sent *to* the list depends
on who/what's running the list server. With debian-user, you get
the Old-Return-Path: which likely resembles the From: header
quoted by John. With gnu.org lists, you see the same information
several times in the Received: lines ("envelope-from" strings)
while the email gets passed into and out of their spam scanner
(whose appropriate hostname is eggs) etc.
Cheers,
David.
Reply to: