Alex van den Bogaerdt writes:
Please explain what being a mutt user has to do with detecting a
difference between rfc821 and rfc2821bis.
Mutt has a command called «bounce» which forwards mail to a third party
without changing existing header fields. Mutt users often describe the
use of that command as «bouncing mail». Among non-mutt users, some seem
to use «bouncing mail» as a synonym for «rejecting mail» and others to
use it in the mutt way. I won't speculate on fraction sizes.
What does this have to with a difference between 2821 and 2821bis?
Nothing per se. It has to do with a difference between reject and
bounce, as mentioned in the subject.