Re: Tcp/Ip vs a store & forward network


Greg Skinner (gds@spam.istc.sri.com)
Tue, 31 Mar 87 20:58:06 -0800


     A reasonable compromise would be a confirmation that the message
     has been placed in the recipients mailbox.

If you'll allow that the message has been placed in the user's maildrop
(/usr/spool/mail/user), sendmail has a feature such that if it receives
mail with the header Return-Receipt-To:, it will generate an ack to the
address listed there. (The address must be replyable from the
receiver's context, so it must contain a full reverse path for a
reliable ack.) You are pretty much guaranteed that the mail has been
committed to stable storage (if not the maildrop, the sendmail spool).

     Presumably, as domain names get extended, we will be able to
     do that. Any mail you send to a user can go directly to the machine
     where the his/her mailbox resides. No forwarding at the site would be
     needed.

I'm not sure what you mean by this. In the ARPA Internet, mail goes
directly from the sender's site to the recipient's site unless
forwarding is specified. UUCP requires forwarding at intermediate
nodes. Even if the UUCP namespace were entirely mapped out, you
couldn't have mail going directly from sender machine to recipient
machine unless everyone called everyone else, which will never happen.

I think we're mixing concepts here a bit. "reliable delivery" to
gds@spam.istc.sri.com is accomplished when something has been delivered
to a process on spam.istc.sri.com which will leave the mail where "gds"
can access it. "reliable delivery" to the human Greg Skinner requires
that he read it. I think it would be asking too much to modify mail
software to require acks, not to mention a problem for sites which don't
have source.

--gregbo



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