At 16:34 -0400 on 06/27/2005, Keith Moore wrote about Re:
Bounce/System Notification Address Verification:
Wrong. There is no prohibition that I'm aware of against using <> for
other purposes, and there are some standards that specifically require
using <> - e.g. MDNs and responses from mail robots, neither of
which are constrained to exactly one recipient.
OTOH: There is no requirement that the generator of these responses
(when presented with a request/need to sent such a message to more
than one recipient) create a single copy of the message as opposed to
one personally addressed copy per recipient. Creating multiple copies
preserves the "Only One Recipient for a 'Mail From <>' message" rule.