ISP port blocking practice

John Levine johnl at
Thu Sep 9 18:33:26 UTC 2010

>That's really the question at hand here -- whether or not there's any
>benefit to continuing the "never ending arms race" game.  Some people
>think there is.  Others question whether anything is really being
>accomplished.  Certainly we're playing it out like an arms race -- ISPs
>block something, spammers find a new way to inject spam, and so on. 
>The end result of lots of time spend on blocking thins, less
>functionality for customers ... but no decrease in spam.

I take it you've never run a mail system other than perhaps a tiny one
for your friends.  The alternative to the arms race is to abandon
e-mail altogether.

>The theory behind closing open relays, blocking port 25, etc., seems to
>(a) That will make it harder on spammers, and that will reduce spam --
>some of the spammers will find other other ways to inject spam, but
>some will just stop, OR
>(b) Eventually, we'll find technical solutions to *all* the ways spam
>is injected, and then there will be no more spam.

Interesting guesses, but wrong.


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