On Tue, 2005-07-05 at 09:10 -0500, wayne wrote:
In
<1120572057(_dot_)19467(_dot_)142(_dot_)camel(_at_)hades(_dot_)cambridge(_dot_)redhat(_dot_)com>
David Woodhouse <dwmw2(_at_)infradead(_dot_)org> writes:
On Tue, 2005-07-05 at 09:53 -0400, Stuart D. Gathman wrote:
Any recipient who rejects your mail because they forwarded it
somewhere else first is badly broken.
You still seem confused. The recipient didn't forward the mail. The
forwarder did. [...]
Any forwarding that is done with out the explicit concent of the
recipient is abusive.
That's your definition maybe, but I don't think you'll find any ISP
including "forwarding of users' mail to the ISP's mailhosts from
elsewhere" under what is defined as 'abuse' in their Acceptable Use
Policy.
But let's not pretend that the administrator of the final recipient's
domain was at all involved in the forwarding process.
The administrator of the final recipient can choose to whether to
support forwarded email or not. If the admin chooses to not support
forwarding, then the recipeient shouldn't foward to that destination.
If they choose to support forwarding, then they should take steps to
support forwarding.
Right. And in general it isn't acceptable for any large mail provider to
_not_ support forwarding, and the only feasible way they can support
forwarding it to refrain from checking SPF. That's the approach which is
taken by most so far.
It isn't just SPF that is causing problems for forwarders in todays
email environment. Anyone who forwards email and doesn't do very
strict anti-spam measures risks being blacklisted as a spam source.
Obviously. That's hardly new.
Forwarding without rewriting the 2821.MAILFROM also causes problems
with bounces because the sender will receive a bounce from some place
that they never sent email to.
That's not a _problem_ though. That's just normal operation. It's worked
that way for years.
It can also increase backscattter.
If the forwarding host has less strict content checking in place than
the final recipient, then it can lead to backscatter, yes.
It _is_ generally content checking which causes this kind of
backscatter, in my experience -- so it's still a potential problem
regardless of SPF, BATV and other tools which attempt to validate the
reverse-path or even mail headers. Thus it's largely irrelevant to the
topic, except of course that BATV users won't be accepting those bounces
if they are generated in response to faked mail.
Besides skipping SPF checks on forwarded email, the final recipient's
domain needs to also skip spam filters/blacklisting, etc.
These are in general perfectly solvable at the forwarding site. You just
make sure your filtering is strict enough that you _don't_ end up
blacklisted, and that in general you aren't forwarding messages with
other sites would reject.
--
dwmw2