[Mailman-Users] cause of bounces

[Dimitri Maziuk]

On 10/18/2017 02:32 PM, Grant Taylor via Mailman-Users wrote:

> I'm referring to the difference between:
> 
>  - ü      - ASCII (?)
>  - =C3=BC - quoted-printable
>  - w7w=   - base 64
>  - ü - HTML
> 
> All four representations are for the *same* letter / character / glyph /
> byte(s).

They are different ASCII representations of the same byte, yes. They are
not the same text. Sign the text, re-encode text and signature together,
anyone who cares about it can decode it back to where the signature will
match. Only, you can't do that on the MX, it has to be done on the client.

> DKIM, by design will fail if anything that is signed changes.

DKIM is designed to produce false positives. Which means DKIM-based
tests will have low specificity
(https://en.wikipedia.org/wiki/Sensitivity_and_specificity). Which makes
them bad for detecting spam. But that's OK, DMARC in general is for
*fraudulent* e-mail, not *unsolicited* e-mail.

I'm sure once I'm plagued by *fraudulent* e-mail, I'll start caring
about RFC 7489 and the rest of them. When those e-mail are from mailman
I'll start caring about what mailman does with DMARC headers. But at
this point I'd just strip them all off.

(And since I'm tripping down the memory lane:
https://catless.ncl.ac.uk/Risks/23/21#subj9.1)

-- 
Dimitri Maziuk
Programmer/sysadmin
BioMagResBank, UW-Madison -- http://www.bmrb.wisc.edu

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