Re: [exim] Bounce Back Envelope From

On Tue, Jul 03, 2018 at 06:46:25AM +0200, Jan Ingvoldstad via Exim-users wrote:
> On Mon, Jul 2, 2018 at 6:40 PM, Bill Cole via Exim-users <
> exim-users@???> wrote:
>
> > On 29 Jun 2018, at 15:30, David Cunningham via Exim-users wrote:
> >
> >
> >> I am using a smart host that will not accept emails from <>.
> >>
> >
> > Are you convinced that "smart" is the right word here? I'm quite certain
> > it is not. Maybe you meant "grossly misconfigured outbound relay" instead?
>
>
> I think another issue to keep in mind is that certain broken e-mail clients
> also send messages with the empty envelope sender in response to spam. "I'm
> on vacation", "This message has been read", "This message has been deleted".

The 2nd and 3d messages may be treated as Message Disposition Notifications
(MDNs), and 1st message may be admittedly assigned to this cathegory too.
All MDNs must be sent from <> address, as RFC3798 says in p.3:

The envelope sender address (i.e., SMTP MAIL FROM) of the MDN MUST be
null (<>), specifying that no Delivery Status Notification messages
or other messages indicating successful or unsuccessful delivery are
to be sent in response to an MDN.

The most impotant reason to treat mentioned messages as MDNs, I think, is
the fact they SHOULD NOT be answered. If such message has user's envelope
address, autoreply or other MDN may be generated, forming mail loop.

So, broken e-mail clients are those that put user's address to envelope
sender for MDNs, particularly Outlook and MS Exchange.
--
Eugene Berdnikov