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Re: [ietf-dkim] Re: ISSUE 1525 -- Restriction to posting by first Author breaks email semantics

2008-01-18 13:16:39
Arvel Hathcock wrote:
hi Jim (and everyone)!

> I'm still missing a suggestion for what we use when the Sender header
> field does not match any of the addresses in the From.  Do we then
> revert to First Author?  All Authors?

The idea of checking SSP on up to N From: domains is the only suggestion I've seen so far and I can't think of anything better.

So, if the SSP algorithm returns Suspicious for any one of the domains found in From: then let that be the final SSP result (in fact, further SSP checks could be skipped at this point). In other words, if even one of the domains listed on the From: requires a verifiable signature and that signature is NOT present then the message is Suspicious even if the result of SSP for one or more of the other domains is non-Suspicious.

Would this work?

It could.

Let me summarize what I think we have consensus on (chairs, please correct me if I'm incorrect because this is your call):

If a message has multiple From addresses, and the Sender address matches one of the From addresses, then the SSP of the Sender address domain is queried. (change from the first From address in the current draft)

What we have left to answer:

If a message has multiple From addresses, and the Sender address does not match one of the From addresses, then I have seen three possibilities proposed:

1.  Use the domain of the first From address
2.  Use the domain of the Sender address
3. Use the domains of all From addresses, and if the message is Suspicious (SSP non-compliant) according to the SSP of any of the From address domains, the message is considered Suspicious (SSP non-compliant).

Note that when I say "Sender address matches..." that means the entire addr-spec of the address (including the local-part, but not the display-name). If you think it should be something else (such as just the domain part) that should be compared, please say so now.

Arvel's suggestion above is #3. I believe Hector earlier favored #2.

-Jim
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