Seth Goodman writes:
Frank Ellermann wrote on Thursday, December 07, 2006 3:58 PM -0600:
Seth Goodman wrote:
SMTP unfortunately does not differentiate between originators
and forwarders.
s/not/not more/ - the original SMTP with reverse paths did this.
[... huge snip ...]
but we are stuck with 821/2821 as they are.
Yes, or 1123/2821, IMO 821 is an innocent bystander in this case.
Good point. These paths contained the routing information so you could
determine who originated a message and who forwarded it.
Only if you believe what SMTP clients claim, and if you believe that,
you can reconstruct the path from the Received headers. I doubt many
people on this list are prepared to put much faith in anything an SMTP
client says.
Trustworthiness issues aside, it's probably worth remembering why mail
forwarding paths were abandoned in the first place. In the days
before 821 and 822, it was unusual for the originating and destination
sites to be directly connected or even part of the same email system.
Mail paths through various gateways had to be specified by the sender
when sending mail. The path you specified could greatly influence how
long it took your mail to get to its destination. Mail rarely
traveled from one relay point to another on demand. Instead, most
relaying was by phone calls and occcurred on a scheduled basis. If
your path got your mail to a gateway just after it completed a call to
the next hop in your path, your mail might wait hours for the next
call. The best path to a destination often depended on the time of
day when you sent the mail, and if you were engaged in anything
resembling rapid email exchanges, you had to know this. Otherwise
email could take days to travel relatively short distances.
The prospect of every originating site being directly connected to
every destination site by the internet was a great leap forward in
email history. Email would travel on demand and might arrive just
moments after being sent, almost as if the remote destination were
next door. The lag in email communication would change from transit
time to time it took for recipients to notice they had mail. Email
could be used by totally non-technical people, because senders would
no longer need to know relaying paths, only destinations.
With the advent of domains, "destination" because an administrative
concept, not a physical concept, further isolating both sender and
recipient from any need to be aware of how mail got from domain to
domain. You could have an address or even multiple addresses in
multiple domains, and your mail would find you. Relaying and
forwarding became things for email administrators to use to make that
happen, not things for senders or recipients to worry about.
--
Dick St.Peters, stpeters(_at_)NetHeaven(_dot_)com
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