Izaac <izaac@setec.org> commented: #I suspect your ISP is also stripping <sarcasm> tags. Let's try it out #again: # # You can tell that tcp port 25 filtering is a highly effective spam # mitigation technique because spam levels have declined in direct # proportion to their level of deployment. Today, we barely see any # spam on the internet due to amazing ability of these filters to # prevent bad people from sending bulk email. # #Was that properly marked? Actually, not sure sarcasm tags are appropriate. 1) Port 25 blocks target direct-to-MX spam delivered by bots. 2) The Spamhaus CBL tracks the level of bot spam currently seen, including breaking out statistics by a number of factors. 3) Currently, the US, where port 25 filtering is routinely deployed by most large ISPs, is ranked 158th among countries when you consider botted users on a per capita basis: http://cbl.abuseat.org/countrypercapita.html 4) While that's not perfect (after all, there are still at least 133,811 listings for the US), on a PER-CAPITA basis, it's not bad -- that's just ~0.055% of US Internet users that are infected, relative to some countries where the rate of detected infection (based on spam emission) may be 4 to 5% or more. So yes, actually, port 25 blocks *DO* tend to be effective in reducing bot-delivered email spam. Does this mean that port 25 blocks are the ONLY measure that is required to control spam? No, absolutely not. But it does clearly help. Regards, Joe