The question is whether AOL.COM has few enough authorized outbound relays
that it fits in a single 512-byte UDP DNS query. I know they can't fit
all their inbounds into one packet, so I suspect the outbounds don't
either.
That is a good point, i believe that the larger ISPs would need to use an
SSL type approach in any case simply to avoid the operational problems
that a mechanism that strongly coupled their outbound mail to the DNS.
I don't see how BCC is meant to create a problem. Any authentication
approach
is authenticating the source of the mail, not the destination.
It is however very useful to distinguish BCC mail from mailing list mail.
I suspect that over time the range of people from whom BCC mail is accepted
will shrink. The range of people I might BCC is pretty small. I would never
BCC someone in a first contact. The main utility in BCC is to avoid creating
ad-hoc mailing lists from reply-to threads...
Phill
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