Re: A new SMTP "3821" [Re: FTC stuff...........]

[Dean Anderson <dean@xxxxxxx>]

On Tue, 7 Dec 2004, David Woodhouse wrote:

> 
> On Mon, 2004-12-06 at 13:11 -0500, Alan DeKok wrote:
> >   You're assuming that messages go from source to destination in one
> > hop.  While this is nice, the current design allows a message to
> > traverse multiple independent hops, all the while using the same "MAIL
> > FROM".  This has a serious impact on the "blowback" problem, and any
> > possible solution.
> 
> I'm not assuming that. I'm saying that SPF doesn't make the problem any
> worse than _other_ schemes will, if they cause the ultimate recipient to
> reject mail which the {backup MX, relay, forwarder} does not reject.

Err, no. SPF does make the blowback problem much worse.  Other schemes 
create a few percent blowback. SPF enables 100% blowback. Thats much 
worse.

> >   Yes, but sharing live information about all of your users with a
> > backup MX is difficult to do in practice. 
> 
> That may be your experience; it's not mine.

That's a general experience with any large mail system. Its also a problem 
where different vendors provide backup mail services.  Its only not a 
problem on simple, small single server systems.


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