On Oct 2, 2007, at 8:48 AM, Scott Kitterman wrote:
On Tuesday 02 October 2007 10:27, Bill(_dot_)Oxley(_at_)cox(_dot_)com wrote:
"A member of a mailing list needs to know two things:
a) did the message come via the mailing list?
b) was it sent to the mailing list by the purported "From"?"
Why would anyone care about b? It is a mailing list which by
nature is
somewhat anonymous and self inclusive. Either a post matches
proper list
content or a moderator will boot the poster with or without warning.
Thanks,
Well, as an example, a message saying:
"There are the following mistakes in the latest SSP draft:
1. ..
2. ..
3. .."
would have a very different meaning coming from me than from Jim
Fenton.
Who is saying something is quite often relevant.
This assertion in what DKIM offers requires fairly flexible
restrictions.
Mailing lists would need to:
- Validate DKIM headers
- Restrict From addresses to be within DKIM domains
- Apply DKIM signatures after flattening
Mailing list recipients would need to:
- Validate DKIM headers
- Restrict Sender addresses to be within DKIM domains
TPA-SSP provides a solution where signatures can invoke tailored
restrictions:
- sub-domain signatures can be authorized as valid
- sub-domain signatures can apply specific scopes
A domain may support a mailing list, transactional email, as well as
allow participants to send messages to a mailing list. Polices
required of DKIM will therefore need to vary or policy will become a
problem. Tailored policies can be structured through use of TPA-
SSP. Dave Crocker once suggested sub-domain signatures be used to
categorize emails. Any signature from a sub-domain is _not_ valid
for an email-address within a parent domain. TPA-SSP can safely
enable a sub-domain strategy as well as any other third-party strategy.
MAIL FROM is also covered by TPA-SSP. Our systems see about 70% of
spam appear as a bounce. (Perhaps soon bouncing entire message
content will be seen as analogous to that of an open proxy.) TPA-SSP
can also make assertions about MAIL FROM email-addresses. This MAIL
FROM assertion might better ensure a DSN is issued rather than dropped.
-Doug
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