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

Peter Viertel wrote:
> Because SPF has the potential to stop the spam from being sent on our network
> in the first place - all the other schemes you mention entail receiving the 
> message
> before making a decision - from a sysadmin's point of view the damage has 
> already been done, the bandwidth has been consumed, the cpu cycles spent.
This is a second order effect. To a first order, the spam problem is 
purely one of human annoyance. If by spending even a fairly large number 
of CPU cycles I can reduce that annoyance even a little, then it's 
almost certainly worth it..
Sysadmins sometimes have to be reminded that computers exist to serve 
humans, not the other way around. And while the cost of compute cycles 
is asymptotically approaching zero, I don't think I read any faster than 
I did in my teens.
> > And I can continue to send my email 
> > direct to its recipients from any IP address I happen to be visiting.
>
> With SMTP Auth set up on your 'home' gateway you should be able to send from 
> anywhere on the Internet via the home gateway, and your emails will look more 
> authentic having come from the right IP.
I find it most curious that everyone is willing to take such extreme 
measures to avoid wasting the tiniest amount of server capacity and 
network bandwith on spam, yet they see no problem in requiring 
legitimate users to waste much of that same server capacity and network 
bandwidth by forcing their traffic through what can be extremely 
suboptimal multihop routes.
If while visiting Australia I send mail to an Australian recipient, why 
should I have to route it back through my home SMTP server in the US 
just to prove that I really sent it? If you want me to prove my mail is 
genuine, my laptop (whose CPU is usually idle) is perfectly capable of 
signing it, resolving the MX records and delivering it directly to its 
destination using whatever IP address it has at the moment. Not only 
does that provide far stronger sender verification than what you 
propose, but it also conserves network bandwidth and server cycles, 
reduces latency and increases reliability. What more could you want?
Phil

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