I observed a similar event on the ietf-edi mailing list a few
weeks ago. Apparently, a list-addressed message had found its
way to the gateway of Aetna Insurance, which responded (to the
list) with a a canned message saying "Thanks for communicating
with us. Please respond with your name and corporate affiliation
so that we may register you in our database", or some such. I
then observed at least ten such dutiful replies (all, of course,
sent to the list as well), and believe it's highly improbable
that all the repliers had spontaneously initiated their own
communications with Aetna and then decided to cc the EDI mailing
list to demonstrate their excitement at having done so. I hope
we're not in for a series of list-addressed messages of the form
"Please continue your registration with CompuSleazyCorp's automated
subsidization facility by returning E-mail with your name, address,
and credit card number", but fear that they also might elicit
some yield in response. Auto-registration is a clever idea,
but sometimes engenders and solicits embarassing results when
the addresses on which it operates correspond to lists or other
entities other than individual people; unfortunately, there's
no uniform means to determine what sort of entity an SMTP address
refers to.
--jl