Jon Kyme wrote:
2. Forwarding is a service provided to recipients in which the
forwarding domain agrees to deliver messages addressed to one mailbox
to another mailbox.
The forwarding case is where the hand-waving comes in. Sender-rewriting
is undesirable here. It means that the intermediary recipient is
essentially forced to present themselves as accountable for a message
that they have no connection to. It also present a heavy burden on many
users who use something like pobox.com or ieee.org to forward to an ISP
account where they have no control over any whitelisting.
I'm not sure from which point of view you judge sender-rewriting
undesirable. It's simply not true that the forwarder has "no connection to"
the messages they forward. The forwarder is not part of, or contracted
with, the recipent ISP, they're as responsible for the messages they submit
as is any other external system. I guess there is added burden for some of
the players here, but they're at liberty not to implement, and suffer some
degradation to their service. This would be an issue for a user who choses
to use a forwarder in an unfriendly environment, and a cost issue for the
forwarder.
I don't see how it's really fair that I should be able to provide services
(and make a profit) in the middle, without taking on some responsibilities
there also.
How about we look at a case where the forwarder has no profit, just cost:
debian.org. Many debian.org users use their addresses as a general purpose
address, with the intention that they will always have it, to forward
wherever they go. Thus, they receive and forward mail coming from all over,
none of which a 3rd party should see them as responsible for. In many
particular cases, that 3rd party is a large ISP corporation that has no
profit motive to let end-users selectively disable filtering of some of
their mail. Thus, debian.org, ostensibly an agent of the recipient, is
forced to bear a cost (taking responsibility for the message in the eyes of
the recipient ISP) in place of the sender.
Perhaps what we need is some standardized way for the recipient/forwarding
user to authorize the message in advance of any filtering. Unfortunately,
that probably won't be effective in this case unless we got an ESMTP
extension designed for it, because ISPs want to filter as early as possible
in the transaction.
Philip Miller
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