In <[log in to unmask]> [log in to unmask] writes:

> This weekend, finally goaded by the spam accumulated over three days'
> absence from the office, I decided to upgrade sendmail on our Internet
> server to 8.9.1, with its more extensive antispam provisions. One of
> those provisions (also available in 8.8.9) is the ability to check the
> Mail Abuse Prevention System (MAPS) Realtime Blackhole List (RBL) server
> in order to reject mail from known spammers and relay sites.
>
> More than half the spam I get comes not through relay sites, but through
> spam generators running on systems connected to the Internet via PPP
> connections. I was under the impression that the RBL contained, among
> other things, the IP addresses that ISPs assign to dial-up ports, since
> legitimate mail relays very rarely use dialup connections. But I've
> checked a number of port addresses that I know are on various ISP
> terminal servers (UUNet, Mindspring and Earthlink, for example), and none
> appear in the RBL. Is there some other server that will allow me to
> reject mail from dial-up relays?

The MAPS/RBL is a *very* conservative list. It only lists long-time repeat
spammers with fixed addresses. In practice nowadays, it stops very little
spam.

There are 4 other popular lists/services to choose from;

ORCA - does dialups
ORBS - blacklists servers that relay unauthenticated mail
IMRSS - same, but proactively searches netblocks for servers to list; many
         more servers, much higher percentageof false positives; very high
         rate of spam-refusal though
DSSL - another dialup list, I believe they also list some cable-modem
       connections, though they've gone back and forth on that. They do have
       a good spam-refusal rate.

<plug> NetMail/3000 and DeskLink users can enable any of these services with
     a simple JCW in the background job, and we were probably the first
     commercial mail server to support all these services </plug>

    -Chris Bartram