kent@xxxxxxxxxxxx a écrit :
On Thu, Apr 17, 2008 at 01:31:49PM -0400, Ugo Bellavance wrote:
There is NO way to prevent people from forging your name to the From: line
on an e-mail message.
False.
No, it's true. There is no way to prevent people from forging the From:
header.
Ok.
SPF can help. DomainKeys can help.
These things help detect forgeries after the fact, but they don't do
anything to prevent forgeries in the From: line. They aren't designed for
that purpose.
Exact, but if the recipients are rejecting messages based on a SPF
hardfail, for example, the result will be that there would be no
backscanner (which is what the OP wanted to prevent).
Some other mechanisms like
watermarking in MailScanner, and there is also something called EMEW in
BarricadeMX (http://www.fsl.com/barricademx.html). There might be other
means, I only know those.
For SPF and DomainKeys, it depends on the proportion of mail servers
that check them.
For the 2 others, it assumes that all of your outgoing mail is going
through the MailScanner/BarricadeMX system(s)
A forged email can come from any server in the world.
What I meant is that with watermarking, any e-mail that comes from the
empty enveloppe, is validated with a watermarking, that allows the
incoming server to determine if the original e-mail that caused the DSN
was originating from itself. If it doesn't it can simply reject it,
still achieving the goal of the OP.
Ugo
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