🚀 go-pugleaf

Long ago in a discussion group not too far away, we discussed one
aspect of this "distribution" problem that I think is relevant in this
current looping discussion.  The original topic was failure return
addresses, and hinged on the question of what is legit for a
distributor to do to a message it is distributing to a list.

Can it ethically and morally change the From: Sender: Reply-to: or
Return-Path: fields to divert mail the might result from downstream
events like failure, or reply, or whatever.

Also, is it a violation of the sanctity of the seal for a LIST
DISTRIBUTOR to look inside the header in the first place.

As I recall the discussion, it was concluded that a LIST DISTRIBUTOR is
in fact operating as a "USER AGENT" and not as a "MAIL TRANSFER AGENT"
so it is fine for the list distributor to do anything its administrator
wants it to do to the content of any distributed item.  If there is any
kind of contract between the administrator and the subscribers, it is
that agreement that governs the administrator's actions.

With this in mind, it seems simple enough to me for any LIST
DISTRIBUTOR to put a special header field (like DIST-ID: <unique-id>)
which is can look for in any incoming item.  If it sees such a thing it
should shunt it aside for manual inspection, and this will prevent
loops through that LIST DISTRIBUTOR, as long as no intervening transfer
agants or user agents or LIST DISTRIBUTORS, et al, remove or change the
magic <unique-id> in any DIST-ID: fields.

This does not take care of other kinds of loops, but it would simply
take care of LIST DISTRIBUTOR LOOPS.

For those of you who are wondering what was decided about the earlier
failure return question, we simply decided to have the list distributor
insert a new "RETURN-PATH: list-request@host" field in place of the
original RETURN-PATH field, without deciding what to do with the old one.

 ---- Stef