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 < > [email protected]> 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. -- ## List details at https://lists.exim.org/mailman/listinfo/exim-users ## Exim details at http://www.exim.org/ ## Please use the Wiki with this list - http://wiki.exim.org/
