Assume that this "new system" you are creating is to be used by
people with current MUAs. Every MUA I am familiar with (the MS
series and the Netscape/Mozilla series) does the same thing when
your "Person B decides to resend": they create a new message,
allowing B to put whatever he/she/it wants to put in it, and
appends the original message (optionally allowing B to add,
subtract, fold, spindle, and mutilate the original content).
This is not a transparent retransmittal of the original message
from A as an MTA would do. Anyone who views this message from B
has no way of determining what, if any, modifications B has made to
the original content.
Server BS _MUST_ treat this as a new message, from B, and sign
as From. How am I wrong, here?
There is a distinction between forwarding a message (which is what
you describe) and re-sending a message (which is what Resent-*
headers are for). Resending /is/ supported by at least some MUAs,
and involves re-submitting the original message to the mail system.
For example, A sends a message to B. B determines that this really
should have gone to C. If B forwards the message and C replies, the
reply goes to B, not A. If B re-sends the message and C replies, the
reply goes to A.
An example is when someone changes roles but is still getting mail
intended for the old role. They want to send old-role messages to
the new person in that role and have it behave as if the message had
originally been sent to the new person --- i.e., they want to wash
their hands of the message entirely.
eric
_______________________________________________
NOTE WELL: This list operates according to
http://mipassoc.org/dkim/ietf-list-rules.html