COX blocking own users outbound email

[jonathan at jonmasters.org (Jon Masters)]

On Sun, 2006-09-03 at 00:29 -0400, Jeff Kinz wrote:

> A few years ago there were heated discussion about whether or not ISP's
> should be blocking SMTP traffic (port 25) from dynamically assigned IP
> addresses.

While on this topic...

There's also a heated debate over whether to block mail from dynamic IP
ranges, such as those commonly used on DSL connections, in anti-spam
blacklists (DNSBLs) on mail servers. Many people believe that those on
DSL should be forced to use their ISP's smarthosts.

Personally, I've just started (this evening) using a few DNS based
blacklist services to screen my inbound mail. I've avoided this
intentionally for the last half a decade, and put up with manually
screening large quantities of mail (with very light sa-exim) in order to
avoid having somebody arbitrarily deciding what mail I should get.

But I've finally given in and decided that a few of these services
explicitly listing known SPAMmers are a good thing. While I disagree
with filtering out dynamic IP ranges on principal, I have discovered
that most of these blacklist services actually split out their filters -
for example, SORBS have a useful blacklist at dnsbl.sorbs.net, but it
includes known dynamic ranges. However, they also maintain:

* smtp.dnsbl.sorbs.net
* web.dnsbl.sorbs.net
* spam.dnsbl.sorbs.net
* zombie.dnsbl.sorbs.net

These are perfectly legitimate blacklisting targets because they cover
"known nasties" rather than just "omg! It's a dynamic IP! get them!".

:-)

Jon.



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