Frank Ellermann wrote:
Frank Ellermann confused "left" and right" :-(
Thus you meant:
BTW, the latest state of the community page
(with only one border) states that anything on
the right hand side is one "MRN". I've no idea
if that is what Keith meant when he coined the
term.
Possibly not. His wording,
A Mail Reception Network (MRN) is a set of
MTAs that accept mail on behalf of a set of
mail domains and deliver each message to
each recipient's message store.
suggests that the set of domains is determined
beforehand, for all messages.
When a "forwarder" enters the picture it is an
MRN, so far it's clear. But to its right it's
an MON sending mail over a second border to a
second MRN.
David insists about the uniqueness of the border.
Perhaps that's not nonsensical as it may appear at
a first glance: There is no second border. The MTA
on the right of a forwarder may alias-expand each
recipient address and forward the message, but it
is still acting within that message's MRN. Each
hop within the MRN must result from a previously
established agreement.
Let's make an example. Message arrives at info [at]
A, forwarded by A to staff [at] B, alias-expanded
by B to x [at] C, y [at] D, z [at] E. B looks up C,
D, and E to find the corresponding MXes and sends
the message in the same way that the original MSA
would have done if the final destinations were
spelled out explicitly from the start. However,
x, y, and z, whether they are individuals, lists,
aliases or whatever, have a forward link configured
at B and thus they must be able to control it. In
particular, they should be able to also control
what policies A enforces.
Making the union of all MRNs that a server may
serve can possibly result in the whole global
network. As configurations may change while a
message is being transported, we cannot even say
that the MRN can be determined in advance. As I
understand it, the point in determining where
the border lies is that spam should be stopped
there.
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