On Mon, 2 Oct 2006, Alan Cox wrote:
>
> Ar Llu, 2006-10-02 am 09:40 -0700, ysgrifennodd Linus Torvalds:
> > If you want a yes/no kind of thing, do it on real hard issues, like not
> > accepting email from machines that aren't registered MX gateways. Sure,
> > that will mean that people who just set up their local sendmail thing and
> > connect directly to port 25 will just not be able to email, but let's face
> > it, that's why we have ISP's and DNS in the first place.
>
> Except most of the ISPs are incompetent and many people have to run
> their own mail system in order to get mail that actually *works*. I've
> had that experience several times, although thankfully I now have a sane
> ISP.
Sure. I kind of agree - I'm just saying that if you have a _hard_
decision, you should base in on _hard_ data.
The MX checking is at least hard, and is a valid reason to just deny
email. I'm not claiming it's "perfect", but it's a hell of a lot better
than bayes.
> MX checking is as broken or more broken than bayes.
I have to say, OSDL has been doing MX checking, and it's effective as
hell. Most importantly, when it _does_ break, it's not because some
"content" is considered inappropriate, it's because some ISP does
something technically wrong.
OSDL also refused to talk to open mail relays etc. I got into something of
a (fairly civilized) shouting match with John Gilmore over it, who used to
send out email from a "fake open mail relay" on princuple (maybe he still
does). He claimed I was censoring his free speech rights when I didn't
read his emails, but I just told him that I was expressing my right to not
listen to people who are so stupid that they can't configure their email
servers.
(I'm not saying that John is stupid, since he did it on purpose, but he
was also clever enough to know exactly what was involved, so it's not like
he couldn't be heard if he wanted to - it's not "censoring" if nobody
listens to you because you built your own sound-proof walls around you).
> There is another reason bayes is not very good too - every good spammer
> reruns their message through spamassassin adding random text till they
> get a good score *then* they spew it out.
Yes. Which is why it's better to rely on hard technical data, or on a
large body of different small rules, including some that are personalized
(ie white-lists and blacklists that are site-specific, including making
things like the bayesian rules be per-site - perhaps _seeded_ by some
common data, but updated locally).
Of course, the MX checking can also be avoided, and a lot of spam-bots
know to use the ISP connection instead of a direct port-25 approach. But
at least that way, the mail gateway can (and often does) notice the
flooding, and many ISP's successfully throttle at least some spam at the
source, so it does actually have real meaning.
Linus
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