On Jan 19, 2007, at 3:29 PM, Paul Hoffman wrote:

At 2:16 PM -0800 1/19/07, Douglas Otis wrote:
Would you explain the reasoning for discouraging verification at the MUA?

No, because that is not what I said, nor is it what I believe. Please do not twist my words, or the words of what are in the spec.

Not every signature will always be checked at the MTA. While the MTA might be focused upon checking signatures that appear linked with the From header, the MUA may ensure Sender headers containing "known" Mailing Lists are always checked, for example. These goals are different, and there is not an expectation that _all_ (if any) signatures are checked at the MTA.

[In particular, deferring verification until the message is accessed by the end user is discouraged.]

One can't say don't check all, as does the added language in the base draft, and then say deferring verification by the end user is discouraged. Clearly this statement seeks to define "deferred" verification efforts at the MUA as being discouraged. This is wrong. Allowing the MUA to only verify signatures linked to trusted email-addresses leaks less information. There might even be valid reasons _not_ to verify signatures at the MTA.

-Doug


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