On Wed, 4 Jul 2018, Jan Ingvoldstad via Exim-users wrote:
> On Wed, Jul 4, 2018 at 9:51 AM, Evgeniy Berdnikov via Exim-users <
> exim-users@???> wrote:
>
> > > 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.
Slightly diverging into the issue of autoreplies;
Don't forget that some systems take regard of other headers in deciding
whether or not to autoreply, which can mitigate some of the potential
backscatter, particularly the RFC3834 Auto-Submitted header and the
Precedence header.
Exchange also has X-Auto-Response-Suppress which another Exchange system,
or something else that has been programmed to pay attention to that
header, can also heed.
I wrote the bulk of this page many years ago on the general topic of
autoreplies:
https://github.com/Exim/exim/wiki/EximAutoReply
If I have control of it, for transactional email, I add something like:
Auto-submitted: auto-generated
X-Auto-Response-Suppress: OOF
Precedence: junk
whether or not it is null sender.
I even look at inbound mail to my site, and if by various criteria I
determine that it shouldn't have an auto-reply sent to it, then I will add
X-Auto-Response-Suppress: OOF, DR, RN, NRN
to the message to discourage our internal Exchange system from generating
an autoreply. Criteria are the presence/content of certain headers (list
auto-submitted and precendence), certain sender address patterns (things
that look like lists, info@, donotreply@ etc) and also certain recipients.
It's all kind of a mess, but lots of the little solutions help the overall
problem.
Jethro.
. . . . . . . . . . . . . . . . . . . . . . . . .
Jethro R Binks, Network Manager,
Information Services Directorate, University Of Strathclyde, Glasgow, UK
The University of Strathclyde is a charitable body, registered in
Scotland, number SC015263.
