ISPs blocking SMTP connections from dynamic IP address space

Michael Conlen meconlen at
Thu Aug 7 10:51:32 PDT 2003

Mykroft Holmes IV wrote:

> These Residential/Dynamic blocks are usually reversed. And they cause 
> the vast majority of problems that originate in North America. 
> Frankly, alot of people simply blacklist 24.* for this reason.
> If your provider's mail servers suck, and they have blocks tagged as 
> Dynamic, and you have no other options, it's time to make a deal with 
> someone to relay your mail for you. 

I've been trying to stay out of this as it has little relation to 
FreeBSD anymore, but blocking 24/8 is simply a bad idea. It's cable 
modem space, not dynamic space. There are a lot of static cable modems 
that are used at businesses.

I've been working on the design of a server based categorization filter 
to be used with IMAP as a local delivery agent on a UNIX system. The 
idea is to use something like the Baysean filter to guess which of your 
email folders mail goes in to. If one of them is Junk mail, there's your 
spam filter. It would also filter all emails from questions at 
in to the same folder I've put all the other emails from the list. I'm 
looking in to which slgorithm to use at this point, as there are several 
that do the same as the Baysean approach and some are supposedly better 
at it.

This filter has the advantage of being server based, but user tunable. 
It will require considerable resources to run as it will require knowing 
the statistics of all your email that you've ever received (at least 
since you started using it), so either it requires that you save all 
your email or it stores token values (and values for strings of tokens) 
in a database.

There's even going to be a way to age values so that as spam evolves it 
keeps up with it.

Michael Conlen

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