On 6/17/2020 9:56 AM, Pete Resnick wrote:
No, the semantics of From: have not changed generally. It's that some mailing lists have to change the semantics of From: in the face of the inability of DMARC to express the semantics that they want.
The two sentences seem to be in conflict. If there is a degree of practice that creates a different semantic for the field, then its semantics have changed, at least for the portion of email traffic.
Here's a simple operational test: MUAs typically can aggregate messages 'from' the same author. After all, that's always been the primary role of From, to indicate who created the content. Such aggregation is usually found to be helpful.
Historically -- for 40+ odd years -- this has worked for mail going through mailing lists. Now it usually doesn't. I'd appreciate an explanation of how that does not constitute a change in semantics.
Have a folder with a variety of messages from correspondents, where some of a person's messages are sent directly to you and some of their messages are sent through mailing lists that adapt the From: field content in order to avoid DMARC rejection. The MUA will handle mail from the same person, but that went through these two different paths, as being from different sources.
DMARC relies on From: because it is the only field with an identifier that is always present. Sender is not reliably present, except virtually. The nature of what DMARC is actually doing looks more like relying on the operations-related Sender: field than the author-related From: field.
DMARC has nothing to do with display of author information to a recipient, and everything to do with differential handling by a receiving filtering engine. Were the Sender: field always present, that would be the one that DMARC should have used.
So, really, DMARC has altered the semantics of the From: field to be the Sender: field. The nature of the hack that mailing lists do, when altering the From: field, makes this clear: They alter information about the operator handling the message, destroying the original information about content authorship.
d/ -- Dave Crocker Brandenburg InternetWorking bbiw.net _______________________________________________ dmarc mailing list dmarc@ietf.org https://www.ietf.org/mailman/listinfo/dmarc
