Re: Why not just use S/MIME or GPG signatures?

Jim Popovitch wrote:

> I have to disagree with this statement.  The Internet, specifically SMTP
> in this case, was never fully intended (nor designed) for direct
> end-to-end email delivery.  It was designed, again speaking about SMTP,
> for reliability and scalability with end users using their upstream
> mailserver(s) for communications.
Say what?

I've been on the Internet almost as long as it has existed, about 20 
years now. Back then, my local client (and server) was a departmental 
VAX-11/780 running BSD UNIX. It ran my (and my colleagues') mail user 
agent, it delivered our outbound mail with SMTP directly to their remote 
destinations (usually other VAXes), and it accepted our inbound mail, 
also with SMTP. Everything was nicely end-to-end. Everybody did it this 
way, because the few personal computers that were around couldn't even 
speak TCP/IP, much less run sendmail.
The notion of the SMTP "mail relay" is still relatively new. Although a 
relaying capability was inherent in sendmail, its first significant use 
(as far as I know) was by Eudora on the Mac, one of the first email 
agents that could run on a personal computer in a disconnected mode. POP 
was also introduced so these agents didn't have to be online all the 
time to receive mail, and that made some sense even though most of the 
Macs I saw sat on desks, never moved or turned off.
But for some reason, the trivial code to resolve MX records and deliver 
*outbound* mail directly to their destinations was never added to 
Eudora. So the relaying of outbound as well as inbound mail 
unfortunately became an entrenched practice when the Internet went 
mainstream. I emphasize this was an accident; it was most certainly not 
how the Internet mail system was originally designed, if only because 
portable, often-disconnected hosts were never seriously considered in 
the original Internet architecture.
> Network routing protocols adhere to this same principal.  Just like, you
> must rely on your upstream provider's gateway to handle packets, you
> should rely on your uptsream provider's email server to deliver your
> email.   
No, they're not the same at all! I have to use my upstream provider's 
router to handle my packets because I have no other neighboring IP 
router to which to send them. But the job of all those routers is to 
form a fully connected network so I can hand off a packet to any IP 
address and have it get there.
It's precisely because IP routers are already designed to form a 
fully-connected network "cloud" that supports end-to-end transparency 
that an additional layer of routing (e.g., at the email layer) is wholly 
unnecessary. The only exception are mobile hosts like laptops that move 
and/or spend much of their time disconnected.
Phil

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