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Re: blocking dialups

  • From: "Clive D.W. Feather" < >
  • Date: Tue, 13 Oct 1998 14:19:17 +0100

torben fjerdingstad said:
>> If you bring this up on SPAMTOOLS-L, you will discover that there is a very
>> diverse range of opinion on the topic. There are *lots* of legitimate uses
>> for direct unrelayed mail.
> Can you mention just one reason for not relay through the ISP's
> mail server (except for sending spam)?

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.
(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.

Oh, plus:

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

>>> Until then, I would like to block all dialup/ppp ip's.
>>> They are easy to find.
>> Oh yes ?
> Just look at the messages from mailer-daemon to find some dialup
> spammers and do reverse lookups for the classe C network they
> came from. I found a nice program for that at
> Sample output:
> =>
> =>
> =>

Which proves what ?

> The hostnames usually clearly indicate if they are dialups.
> Try to ping a few of them for verification. Or telnet
> to the smtp port if really in doubt.

And what did you get for the above three ?


Clive D.W. Feather       | Email: clive@localhost   | Tel: +44 1733 705000
Regulation Officer       | Home:  clive@localhost |  or: +44 973 377646
London Internet Exchange |                           | Fax: +44 1733 353929

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