> On Feb 28, 2019, at 9:11 PM, Benjamin Kaduk <ka...@mit.edu> wrote:
>
>> The primary motivation for "Require TLS = no" is to allow the user
>> to *resend" a message that is not getting through, or to reach the
>> destination domain's postmaster because of downstream (receiving
>> system misconfiguration), to send a message that requires no meaningful
>> confidentiality. Individual users are very well positioned to make
>
> If those are the *primary motivation*s, then why does neither "resend" nor
> "postmaster" appear in the -07?
Well, for me (can't speak for others), it did not seem like an important
detail. The mechanism is independent of what one might guess to be the
user's most likely motives. Perhaps these should have been explicit,
but they seemed obvious and inessential. :-(
The idea is that the recipient's promise to have working TLS with either
DANE, MTA-STS or both might not always work out, and so users as well as
MTA administrators might sometimes need a plan B. The individual user
is generally well placed to make a judgement call about the sensitivity
of his message.
That may not be true for "corporate citizens", but the corporate SMTP
gateway is controlled by the organization, not the user, and is free to
not honour the user's signal, like any signal from remote MTAs, this
signal from the user is input to local policy, not a mandate.
Only "RequireTLS = yes" imposes a clear mandate on conformant MTAs.
--
Viktor.
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