Re: [ietf-smtp] Email standard revision, was address maximum length

On 11/29/2019 6:12 PM, John C Klensin wrote:
> > Even the "From: rewriting" issue is
> > a gatewaying issue, not a message format issue per se.
> That is less clear.  It fits into the gray area that has existed
> for years about just exactly what a mailing list exploder /
> redistribution system really is.  We've traditionally threaded
> that needle by saying that, if the message is simply
> redistributed, without messing with content (or headers other
> than trace ones), then it is an SMTP matter, and that is what
> 5321 talks about.
+1.

The separation problem can be felt depending on where the transaction 
payload processing is performed - Post SMTP or Dynamic SMTP processing.
With post-smtp processing, messages are first accepted at DATA and 
from the SMTP client perspective, the transaction is complete. The 
RFC5322 payload is queued for independent processors which could be a 
MDA, a MLS (Mailing List Server), a MFA (Mail Filtering Agent) or a 
gateway to a different mail format and even network.  These post mail 
agents probably also worked (ours did) in the UUCP days and were made 
to fit with SMTP when SMTP replaced UUCICO/UUCP mail transfer methods.
Once dynamic DATA processing became feasible (due to higher processing 
power and speeds allowing for fast shiming, hooking, running milters 
at the DATA state), it was now an 5321 issue because now it 
necessitated new security-related reply codes and responses.  With 
negative responses related to restrictive DKIM Author Domain Signature 
Practices, it could cause list problems that precipitated the "what 
choice do I have, the IETF has punted on this problem" 5322.Rewrite logic.
Besides accepting the appalling suggestion "5322.From Rewriting" is 
normal (list) practice today, I don't believe it is, the problem is it 
takes a secured domain message, rewrites the From: domain to correct 
the list distribution but it now opens a security loophole for the 
original domain with replays.

--
HLS


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