On 8/9/2023 7:55 AM, Murray S. Kucherawy wrote:
I have heard, but have not verified, that some MLMs do this one-recipient-per-copy thing already, despite RFC 5321 encouraging the opposite. If true, I don't know whether this was done to allow per-instance signing or because it allows for better tracking and association of bounces, or for some other reason. It occurs to me that unless the Date field changes for each instance, the DKIM signature would be the same for each instance anyway.
Bulk mailers tend to do one-per, because each is tagged to the recipient, for tracking.
Consequently, the advice you cite conforms to the original intent of having SMTP -- the FTP mail/mlfl functions were one-per and SMTP introduced multiple recipients -- but that efficiency has largely been superseded by other goals.
d/ -- Dave Crocker Brandenburg InternetWorking bbiw.net mast:@dcrocker@mastodon.social _______________________________________________ Ietf-dkim mailing list Ietf-dkim@ietf.org https://www.ietf.org/mailman/listinfo/ietf-dkim
