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

2019-11-30 10:49:46
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.


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.


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