Re: blocking dialups

[torben fjerdingstad <]

I feel pretty alone on this issue. What I was looking for was a
way to know when dialup ip's get allocated for other purposes.
Now, it's time for my last comments on this thread. Thanks.

On Tue, Oct 13, 1998 at 02:19:15PM +0200, Martin Lorensen wrote:
> On Tue, 13 Oct 1998, torben fjerdingstad wrote:
> > Can you mention just one reason for not relay through the ISP's
> > mail server (except for sending spam)?
> 
>  - Don't known the ISP's mailserver name (Roaming/IPass)

A good one. I don't know how that works or how to deal with it.

>  - Running Linux server with sendmail.

Bad one. sendmail requires a fixed connection. If it is an isdn
dialup, it benefits by letting the ISP's mail server do the
hard work with slow deliveries, timeouts and retries.
If it's a fixed line, it's not a dialup.

>  - Connects to diffrent ISP's.

I don't see the point. Roaming?

"Clive D.W. Feather" clive@localhost added:
> Here's two:

> (1) You are then reliant on the ISP's mail server; if that breaks in any
> way, you're dead in the water.

I would feel a lot more dead if I had to waste phone costs retrying
for days to do a delivery to santa claus, because his server is
flooded.

Note. Our mail server has been 100% reliable since I installed
it on aug. 19. 1997.

> (2) A closed user group can authenticate mail to addresses based on the
> sender address; for example, I can email certain internal lists from my
> dialup, but not everyone else can.

I hope sender address means the ip address. Why would you want to
be able to deliver those mails to us?

> Oh, plus:

> (0) I buy access to the *Internet* from my ISP, not access to their
> intranet.

I can't imagine how two dialup customers at that ISP can mail each
other without a mail server at the ISP. Well, they could use pop3,
but we are talking about smtp here.

>> Sample output:
>> 195.66.232.18 => guest1.linx.org

> Which proves what ?

Nothing. It's just a sample output.

> Try:
>     romana.davros.org
>     stdc.demon.co.uk
>     on-the-train.demon.co.uk

Since you ask I assume they are dialups. But they have not sent
me spam, so I have no reason to block them.

The directly sent spams I have seen came from large ISP's who have
whole class C networks allocated for dialups. I'm not so worried
about the rest of them.

-- 
Med venlig hilsen / Regards 
Netdriftgruppen / Network Management Group
UNI-C          

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