More specifically, there can be legal requirements for all message
recipients to be listed in the header. Just putting in the address of
a mailing list is unaccepatable because the content of that list can
vary over time. Depending on the specific requirements in a given
jurisdiction, it may be necessary to expand the list into the header
- alternative schemes such as keeping a precide revision history for
the list, or accurate logs of message traffic, while technically OK,
may not be allosed. (These systems typically also impose draconian
restrictions on forwarding, but that's a separate matter.)
I can understand why each of the recipients might need to know who
else got the message, but why would the list have to be in the header
rather than, say, at the end of the message body?
R's,
John