Re: Discrimination by IP address

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• In reply to: Susan Bradley, CPA aka Ebitz - SBS Rocks [MVP]: "Re: Discrimination by IP address"
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Date: Sun, 8 Aug 2004 09:12:18 +0100

I have recently had issues with rejected email.
Common anti-spam organisations like sorbs.net and spamhouse.org run
blacklists. Spam is also registered on a range of addresses if they used to
be in a pool of dynamic addresses, issued by an ISP.
I have a client that was given a static IP address, and around 8 months
before they'd received it, that IP address was registered by sorbs.net as a
source of spam. (I think it used to be a dynamic address). For the majority
of outgoing mail, the delivery is received by the addressee, but anyone
subscribing to these spam agencies reject the email. Getting the ISP to talk
to Sorbs is difficult but de-registration is possible.
I wasn't sure how to solve it on SBS2003, but with a short conversation with
the ISP and a small change in CEICW, the client is very happy that his email
is no longer being rejected.
The change was made by not using DNS to send email, but to forward the email
to the ISPs mail forwarding server, where they will relay it out for you.
Because the mail forwarder has proper registered IP addresses, they don't
appear on spam lists.
Each ISP would probably have this facility, I suppose - a particular server
address was provided by the ISP.
I know what Mr Long is referring to. But when someone has abused the source
address...what can you do, except find a workaround. Please don't take it
personally. I might filter spam and reject messages but I cannot tell from
the incoming message that it originates from a person of good personal
integrity, like Tim Long. Its the same adage as before. Eternal
vigilance....etc...

"Susan Bradley, CPA aka Ebitz - SBS Rocks [MVP]" <sbradcpa@pacbell.net>
wrote in message news:u8g0d1LfEHA.2000@tk2msftngp13.phx.gbl...
> We don't have a choice it's the ISP's that are doing it. :-(
>
> Tim Long wrote:
>
> > Here's a post I just put on my blog at
> > http://syd.tigranetworks.co.uk/TimBlog/
> > Maybe it will provoke some discussion here. What do all you technology
> > consultants think about my opinions on filtering by IP address?
> > --Tim Long
> >
> > ===============================================
> >
> > Yes, I do use a dynamic IP and no, I'm not a spammer. Why do some people
> > reject my email simply because my IP address is dynamic?
> >
> > The assumption is that most spammers use dynamic IP addresses (to cover
> > their tracks) therefore all email from dynamic IPs must be bad.
> >
> > Hang on a minute, isn't that a tad like discrimination by skin colour?
How
> > is that different from saying something like "Most spammers live in
Elbonia
> > so we'll block all email from that country"? Blocking an email based in
the
> > flavour of its IP address is at best totally arbitrary and at worst,
> > discriminatory and downright offensive.
> >
> > I personally object to being filtered based on my IP address. This is a
> > practice that ISPs seem keen to promote, presumably because it benefits
them
> > when users have to pay extra for a static IP. The final irony is that
it's
> > meaningless to filter by type of IP address anyway, since there are
many
> > open relays and free SMTP services with static IPs that anyone can sign
up
> > to using fake details. Any competent spammer will know about these.
> >
> > Another problem with dynamic IP blocking is that the user of the IP
address
> > has no right of reply. The censorship is summarily imposed and there is
no
> > right of appeal. I have no way to prove I'm a legitimate sender of
email.
> >
> > Dynamic DNS is a growing market arising from ISP's reluctance to
permanently
> > assign ever-scarcer IPv4 addresses. A static IP usually costs extra and
in
> > some cases is not even available at all. Any why should it be? Dynamic
DNS
> > is a perfectly good solution. Dynamic DNS providers are becoming more
common
> > as more and more broadband users rebel against the limitations of their
DSL
> > provider. Home users and even small businesses are using Dynamic IP
> > addresses. Perhaps this will change once IPv6 becomes the norm, but that
is
> > way off.
> >
> > So before we go around filtering people based on arbitrary criteria
which
> > are guaranteed to be wrong a good percentage of the time, what else can
be
> > done?
> >
> > a.. Bayesian analysis - my server's anti-spam reports show
conclusivley
> > that this technique catches the most spam and yields the lowest number
of
> > false positives. I use GFI Mail Essentials for Exchange Server, but
there
> > are other alternatives. For example, there is a product called InBoxer
for
> > stand-alone Outlook installations. There are also open source systems.
> > b.. Keyword checking - also effective in many situations but must be
used
> > with care to avoid too many false positives.
> > c.. DNSBL - A better alternative to filtering by the type of IP
address
> > because it at least requires the originator to have been accused of
sending
> > spam and provides a mechanism for legitimate users to get themselves
removed
> > from the database. Dynamic DNS filters have no avenue of recourse for
> > legitimate users.
> > So I'm asking SysAdmins to please think long and hard before they apply
> > arbitrary filtering rules to incoming email and whether those rules
really
> > achieve the objective of keeping your systems spam-free.
> >
> >
> >
> > --Tim Long
> >
> >
>
> --
> http://www.sbslinks.com/really.htm

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• In reply to: Susan Bradley, CPA aka Ebitz - SBS Rocks [MVP]: "Re: Discrimination by IP address"
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