On Wed, Jul 4, 2018 at 9:51 AM, Evgeniy Berdnikov via Exim-users <
exim-users@???> wrote:
> 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.
>
No, Outlook does not do this. Outlook is one of those who, brokenly, send
MDNs, generating backscatter.
Maybe MS Exchange can be configured to generate backscatter similarly, I
don't know.
--
Jan
