At 7:32 AM -0400 2003/09/10, Marc A. Pelletier wrote:
b) Some way of delegating. 'us.example.com' may well have different
administrators and mail policies than 'jp.example.com' in addition to
being
on different continents.
Indeed. You can't really co-opt mx.example.com as the subdomain
to use to specify the outbound mail servers, because many companies
have subdomains per-country, and ".mx" is a valid ccTLD -- Mexico.
I realized this a couple of months after we chose mx.aol.com as
the subdomain to handle all inbound MX records for AOL -- we were
screwed if we ever got a Mexican service.
You also can't really co-opt a name like relay.example.net and
then list all IP addresses of all officially known mail servers,
because some sites use that as their customer-visible name for their
outbound mail relays.
Moreover, some sites will put that IP address on a load-balancing
switch, although the servers behind the switch will use their real IP
addresses for their outbound connections (which might be on a
different interface, and would obviously have to be completely
different from the customer-advertised address).
And there remain all the problems with legitimate third-party
relay activity, which have been previously discussed.
--
Brad Knowles, <brad(_dot_)knowles(_at_)skynet(_dot_)be>
"They that can give up essential liberty to obtain a little temporary
safety deserve neither liberty nor safety."
-Benjamin Franklin, Historical Review of Pennsylvania.
GCS/IT d+(-) s:+(++)>: a C++(+++)$ UMBSHI++++$ P+>++ L+ !E-(---) W+++(--) N+
!w--- O- M++ V PS++(+++) PE- Y+(++) PGP>+++ t+(+++) 5++(+++) X++(+++) R+(+++)
tv+(+++) b+(++++) DI+(++++) D+(++) G+(++++) e++>++++ h--- r---(+++)* z(+++)
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