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Re: [ietf-smtp] Email explained from first principles

2021-05-23 07:16:16
Dear Bron,

Thanks a lot for your response and please excuse my late reply.

On 17 May 2021, at 03:33, Bron Gondwana <brong(_at_)fastmailteam(_dot_)com> 
wrote:
It's clear you've put a lot of work into putting this together.  
Unfortunately I don't have time right now to do it justice and review the 
whole thing!  I'm not sure that anyone else is likely to either.  This is one 
of the ongoing challenges for any work, it's more interesting to do the work 
than to review it!

Yes, I totally understand this. While I asked for feedback and criticism, I 
also shared my work with this mailing list for two other reasons:

1. My work could be really useful to the IETF community by allowing you to 
refer people to this comprehensive introduction to modern email. (For some 
people here, it’s also a summary of and a tribute to their life’s work.)

2. I’m very much aware of the epistemic damage one can cause as an author, and 
I take this responsibility seriously. For example, confusing opportunistic use 
of TLS with explicit use of TLS was a big mistake. I don’t know who started 
this, but I tried my best to rectify this misconception. If my article becomes 
the definitive guide to email for newcomers (I know that this is a big “if”), 
any error in my text can cause a lot of work for people on this mailing list. 
Differing terminology is a good example of harm I might cause to the email 
community, and I’ve already received two remarks in this direction.

But that actually raises the more interesting question out of all of this.  
Are you interested in engaging with the IETF community and helping to 
progress your ideas within the IETF?  Because that's going to involve the 
messiness of human interaction and building relationships so that people make 
the time to review your work because they know you will return the favour 
when they need reviews

You raise a valid point. I don’t mind the messiness of human interactions and I 
can imagine getting involved in some IETF efforts. I’m somewhat hesitant for 
two reasons:

1. I might be wrong, but my impression is that most people are paid for their 
standardization work by a company or a university. I won’t be able to 
contribute a significant amount of work unless an organization is willing to 
sponsor me.

2. Standards alone don’t matter. During my research, I learned about many great 
standards which haven’t found significant adoption yet. Examples of this are 
SRV records for autoconfiguration and the REQUIRETLS extension to ESMTP. 
Innovation has to be driven by the relevant players in the field, and I’m not 
one of them.

Having said this, I’d be open to work on the following, relatively low hanging 
fruits if enough people here encourage me to do so:

1. Formalizing no reply: Many automated systems send emails but cannot handle 
replies. A new RFC could either acknowledge that no reply shall be sent if the 
local part of the sender is “no-reply” or introduce a new header field to 
achieve the same. (See 
https://explained-from-first-principles.com/email/#no-reply 
<https://explained-from-first-principles.com/email/#no-reply> for more context. 
The idea is that mail clients wouldn’t even offer a reply button for such 
messages.)

2. List-Name header field: Mailing lists shouldn’t rewrite the messages of 
others and break DKIM signatures in the process. Since my email address was 
rewritten due to my domain policy, I didn’t receive some of the replies to my 
original message because I didn’t subscribe to this mailing list immediately. 
The List-Unsubscribe header field makes it unnecessary to include an 
unsubscribe footer in forwarded messages. A new List-Name header field would 
make it unnecessary to prefix the Subject with the name of the list. Mail 
clients could simply prefix the Subject with the value of the List-Name header 
field according to the user’s preferences locally if desired. Anyone who moves 
messages to separate folders with filtering rules might not even be interested 
in this. In my opinion, DKIM signatures are broken for no good reason.

I wonder if you'd be interested in the work happening in the GNAP working 
group.

Thanks for the hint, I wasn’t aware of this working group.

2. SMTP for Submission should make it clear that the IP address of the 
submitter SHOULD NOT be included in the Received header field. In my view, 
the current practice of many email service providers violates the European 
General Data Protection Regulation (GDPR): 
https://explained-from-first-principles.com/email/#sender-towards-recipients 
<https://explained-from-first-principles.com/email/#sender-towards-recipients>

This is an interesting question.  Are you entitled to such privacy from the 
recipient?  If so, on what basis?  This kind of thing is very much a tradeoff 
of various concerns, and by removing your IP address, the server to which you 
are making the submission is taking on additional responsibility for the 
content of your message.

Leaking the IP address of the sender to the recipient has serious implications 
for privacy (geolocation of the sender and tracking the sender across services) 
and security (denial-of-service attacks and targeted remote attacks). With 
broadband Internet, many households have the same IP address for months or even 
years. As a consequence, IP addresses are justifiably treated as personally 
identifiable information. Given laws such as GDPR, many lawmakers think that 
I’m entitled to such privacy. For similar reasons, some companies proxy remote 
content for their users (see 
https://explained-from-first-principles.com/email/#proxying-remote-content 
<https://explained-from-first-principles.com/email/#proxying-remote-content>), 
but this is pointless if they share the user’s IP address when the user hits on 
“reply”. And as far as reputation and domain authentication are concerned, 
outgoing mail servers take responsibility for my messages anyway. (To be clear: 
I don’t mind if companies keep logs of email submissions. There’s just no 
reason to share the most confidential part of such logs with all recipients.)

[Remote content]

But upgrading from where we are to there is a big project - who's going to do 
the work?  Both in defining something better, and persuading the world to 
move to it.  These are both hard problems, because the something better needs 
to be persuasive.

I don’t have the answer either, but convincing authors of mail clients to 
disable remote content by default seems like a good place to start. :-) (And we 
already have “something better” in the form of aggregate documents: 
https://explained-from-first-principles.com/email/#aggregate-documents 
<https://explained-from-first-principles.com/email/#aggregate-documents>.)

7. I don't understand why Authenticated Received Chain (ARC) is necessary or 
even desirable: 
https://explained-from-first-principles.com/email/#authenticated-received-chain
 
<https://explained-from-first-principles.com/email/#authenticated-received-chain>

It's an attempt to solve the mailing list problem and the forwarder problem.  
At least for pure forwarding the simple solution is to keep the bytes intact 
so that DKIM still passes, but for messages without DKIM it will at least 
maintain some integrity tracking on the SPF check that was done when it 
entered ARC-supporting servers.

Yes, I understand this, but the forwarding mail system could just add a DKIM 
signature using its own domain and take responsibility for the message (as 
mentioned by the DKIM RFC if I remember correctly). Recipients are free to 
trust such signatures.

There's a discussion in the IETF generally about how to deal with the backlog 
of errata.  Again as I mentioned right up the top - getting people to do the 
boring grunt work of reading others' work and providing insightful feedback 
is tricky!  Finding time to process things is tricky.

Here is what I replied to someone from this mailing list who contacted me 
privately:

It would be valuable if RFCs could reflect the current (and original) sentiment 
of IETF members. A designation, such as “deprecated” or “no longer maintained”, 
could help external people like me a lot. You could also stop accepting errata 
for such RFCs then. And to most of my errata, I did get a response (see 
https://mailarchive.ietf.org/arch/search/?q=Kaspar%20Etter 
<https://mailarchive.ietf.org/arch/search/?q=Kaspar%20Etter>). But while it’s 
easy to find an RFC and its errata, it’s difficult for others to find the 
corresponding conversation. Automatically referencing the corresponding thread 
in the mail archive would go a long way towards making RFCs and their errata 
more accessible to outsiders.

Clearly you've found an enormous amount of time to put all this together, and 
it's really excellent work.  It feels like the kind of thing that you should 
be getting academic credit for, to the extend of being a published paper, at 
least to the "Honours Degree" level - it's carefully researched and 
meticulous.

Thank you for this compliment.

I hope you have the time and the willingness to engage with the IETF 
community as a contributor and to work within the ebb-and-flow of human 
relationships to progress some of your ideas and your work further.  We could 
do with the energy that you're bringing - it's just a lot to bite off so much 
all in one go!

See my reply above. If someone has the capacity to mentor me, I’m confident 
that we can make something happen. :-)

Best regards,
Kaspar

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