On Tue, 2002-11-26 at 09:39, Fredrik Söderblom wrote:
> From: "Frey Sigurjonsson" <[log in to unmask]>
> To: Fredrik Söderblom <[log in to unmask]>
> Date: Tue, 26 Nov 2002 09:07:20 +0100
> They're wrong when they say that SPAM within the own network is not a problem, it is.
> A lot of our customers has implemented SMTP servers with default (ie: sendmail's DS=) relay
> to Song's systems. When the customers SMTP servers doesn't have adequate relay protection they get
> abused by spammers. That results in the customers system, and in some cases even songs systems, get's
> blacklisted. Song, since we obviously have been part of the SPAM (for a domain we don't handle).
> The blacklisting itself results in problems for all users.
This is quite a common problem though, an ISP's SMTP-server being listed
in various spam-blacklists, usually for being a second-level relay (i.e.
a customers open relay defaults to sending mail through the ISP's
mailserver who happily accepts them), or in other ways being listed
because of something done on a customers mailserver, that is really
outside the realm of their control.
I personally do not think implementing forced pop-before-smtp from ones
own netblocks is a very good idea though, there are plenty of customers
who legitimately use the default-method to dump their outbound mail onto
the ISP's servers, or as in the case here, get POP/IMAP services from
If one wants to avoid the second-level relay problem (or similar), a
better idea would probably be if the ISP's own mailservers blackholed
mail from the offending customer servers directly, by using some of
these same lists - when the customers can't get their mails through,
they are usually quite quick in calling support, where you can then
quickly establish that the customers clueless admins must clean up their
act (i.e. fix their servers and get off the necessary blackhole-lists)
before their mail starts working again.
But that's just my personal opinion on this, I would never use my ISP's
mailservers anyway (not even those of my own employer :)