Yesterday I read an article about the fact that a couple of Dutch ISP’s now block ’spam’ port 25. Port 25 is nothing more than your SMTP port, which probably is exploited by botnet-admins to send loads and loads of spam.
So now all of their customers have to suffer, which is overkill, for the few customers that have insecure, infected systems. Luckily my ISP is ’smart’, which the others are clearly not, because they monitor the traffic on port 25 and block specific customers which send spam. At the end of the day I’m glad I pay a buck a month more, but I’m also getting a better service for it!