Re: [cobalt-users] Spam blocking

[David Lucas <david@xxxxxxxxxxxxxxxx>]

At 07:38 PM 1/21/2004, you wrote:
> Reading over the last few days threads regarding spam blocking I've noticed
> references to a large number of RBLs and a number of implementations of
> same. It's nice to see that people want to block spam, but you need to be
> VERY careful how you do this.
>
> You may reduce your spam by 75% if you add in three or four RBLs at the MTA
> level, but you are also going to block a lot of legitamate email in the
> process if you are blindly grabbing tips of mailing lists.

I seriously doubt that you are going to block a log of legitimate 
email.  Yes you may block some.

> I do not mean to be facetious about this, but if you are handling email for
> a large number of users (ie not just you and your personal friends) you
> could be placing yourself in a very precarious position.
>
> Each RBL follows its own set of criteria. Some are very extreme (dynamic IP
> blocks for example), while others may be blocking entire subnets based on
> the netblock owner (or its predecessor).

This point is very true.  At this point in time, anyone using a dynamic IP 
address to send their own mail should be considered nuts.  So many servers 
are now blocking email from dynamic IP addresses, it is a wonder that any 
of their email is getting through.  It is turning out that ISP's are 
winning here and it is best is people send their email out via the SMTP 
server of their ISP.

> If you are handling mail for third parties, as would be the case of hosting
> companies etc., you may must not forget that you are as likely to be held
> liable for the mail not delivered as the mail that is.

If you modify the refusal statement and provide a web page of your own with 
a form for the person to notify you, you can make adjustments when contacted.

> So do not blindly add RBLs to your servers unless you know what you are
> doing.

People shouldn't do anything to their server unless they know what they are 
doing. Duh!



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