Stuart D. Gathman wrote on Saturday, March 17, 2007 7:23 AM -0600:
On Fri, 16 Mar 2007, Seth Goodman wrote:
Since large systems are unlikely to whitelist forwarders per user,
and global forwarder whitelisting means too much additional spam,
the recommended best practice is not realistic for large systems.
Large systems that I am familiar with (e.g. spamsoap.com) *already*
whitelist senders per user. The only change required is to
flag some senders as forwarders and apply the "pretend" sender rule.
Most systems have to whitelist some senders, and some do so per user,
but I'm unaware of any large systems that whitelist forwarders per user.
In most cases of sender whitelisting per user, this happens
automatically when the user sends mail to a destination mailbox, so the
user's own forwarders are never listed. Compiling and maintaining a
forwarder whitelist per user is not the trivial exercise you suggest, it
is a major adoption hurdle. Forwarding will not go away because it is
technically flawed, and large services are not going to sign up for
something that their users perceive as annoying and involves significant
I still believe that the best practice recommendation for large systems
Sender Policy Framework: http://www.openspf.org/
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