On Sep 5, 2010, at 10:36 AM, Claudio Lapidus wrote: > Hello all, > > On Fri, Sep 3, 2010 at 11:30 PM, Ricky Beam <jfb...@gmail.com> wrote: >> >> If I block port 25 on my network, no spam will originate from it. >> (probablly) The spammers will move on to a network that doesn't block their >> crap. As long as there are such open networks, spam will be rampant. If, >> overnight, every network filtered port 25, spam would all but disappear. >> But spam would not completely disappear -- it would just be coming from >> known mailservers :-) thus enters outbound scanning and the frustrated user >> complaints from poorly tuned systems... >> > > That won't be probably the case. Here recently we conducted a rather > comprehensive analysis on dns activity from subscribers, and we've > found that in IP ranges that already have outgoing 25 blocked we were > still getting complaints about originating spam. It turned out that > the bots also know how to send through webmail, so port 25 blocking > renders ineffective there. > > --cl.
Perhaps a new BCP is coming from MAAWG suggesting we now block outbound port 80. Owen