Mariano,
SURBL is not meant for blocking porn unless it is also spam **And** unless the domain is NOT also found in legitimate (abet porn) e-mails. Not this these don't qualify... they may very well be good candidates for SURBL... but the fact that they were porn and found in spam is not enough. There would also have to be a determination that these are not found in non-spam porn mail. Other factors would include how egregious is the domain owner at spamming (NANAS & SpamHaus.org records, for example).
If porn-mail blocking is a concern of yours, I suggest that you use the porn blocking dnsbl found at http://rhs.mailpolice.com/. It works just like SURBL, except that it applies to domains only (not IP addresses) and, as I said, they list porn domains REGARDLESS of whether or not they are found in spam.
MailPolice.com also has a combined blocklist which merges their spam block list with their porn block list. It is also very good and catches some stuff that SURBL doesn't catch. However, be warned... it also generates some False Positives. (But not nearly as bad as some other do). I use the general blocklist (spam & porn) and I manually override the FPs as they occur to prevent them from being blocked again.
Also, as I said, both work on domains found with the message (just like SURBL, except that SURBL also lists IP addresses). These are NOT MTA-blocking RBL's.
Hope this helps!
(BTW - does anyone know of any OTHER such porn-blocking DNSBLs, like the one at mailpolice.com???)
Rob McEwen