Charles Lindsey wrote:
The only place where it is known that a crosspost is occurring is at the
original sender.
Not true, on at least two counts:
1. an author might not know that a particular mailbox expands to a list.
Indeed, the list manager might not know! [I recall a case where one
of the GNU bog reporting mailboxes was a list expander, and that
expander for a time sent out complaints (to the From field, not the
envelope sender address or Reply-To, or Sender) that the domain name
had changed -- the domain was the one put in by the expander and it
turned out that that was the very site that was also generating the
complaints.]
2. In the case of a mailing list expander where one of the expansion
mailboxes is a list submission mailbox, the maintainer of the
first list expander might indeed know that another list is being fed.
Therefore, any information to inform subsequent agents
that crossposting is afoot HAS to be placed in the message by the original
sender.
Bad conclusion based on a false premise.
The MFT proposal at least provides a possibility for the original sender
to specify such information.
Which proposal? I haven't seen one that states that MFT "indicates that
a crosspost is occurring".