Arnt Gulbrandsen writes:
But IMO, the list processor software is a recipient as far as the
internet mail system is concerned. (You get a final delivery DSN when
the message is delivered to the mailing list processor.)
Let me put it differently.
A sender should either expect the recipient to use the label, or else
put in application/octet-stream.
Saying things like "the label is useful and should be there, but only
human recipients should use it, programs should ignore it" is IMO
nonsensical. I hope I'm not erecting strawmen.