On 12/6/20 5:40 AM, Alessandro Vesely wrote:
On Sun 06/Dec/2020 02:34:45 +0100 Michael Thomas wrote:

5) The work you and Alessandro have done with reverse transformation is more likely to produce a solution for the mailing lists.   The lists will continue to do From rewrite, but reverse-transform recipients can validate the true source of the message and restore the From if desired.

I'm starting to get a little more serious about my quip that the MLM can insert a sed script in a header to unmangle the message since it knows what transforms it has done, unlike the receiving MTA trying to guess the common transformations.


But then the receiving MTA will have to guess whether the sed script considerably alters the intended meaning of the message. For example, does it change a bank account number?

This actually highlights why my observation is correct. If the intermediary showed how to reverse their changes perfectly to be able to validate the original signature, it says nothing about whether those changes to be delivered to the recipient are acceptable to the originating domain. for the case of a bank sending me sensitive mail, the answer is that it is never ok. for somebody working on internet standards working on ietf lists, the answer is that it is fine. hence trying to get two states of the one "reject" is insufficient.

Mike

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