Well one problem is that we need a new email system and no one wants to make the move.
i was on a volunteer internet working group on how to deal with spam back in the late end of the 1990's
about 1998 i think.
when i pointed out that smtp had some very basic issues that should be changed the majority of the folks on the group said that was not whyat they would support, that the anti spam extesions had to work within smtp as it was.
well after that i dropped off the list cause they were not going to fix the real problem.
the issues are not trivial.
think of how many smtp servers there are in the world right now.... a lot....
as for blocking the smtp port... actually i have no problem as long as the isp has a policy of allowing you to request that your connection be open.
see one of the problems is that *if* an isp lets all traffice thru then pc's on that network can all become mail servers ...
if for example a trojan / bot control program gets even a few hundred pc's sending spam from that network then it becomes a real problem for the isp and the global email community.
while i want the internet to be very open i also think that if you are on a network you have to play within some limits.
the network operator should be able to limit the number of mail servers - not to keep you from sending email but to keep bot nets from flooding the network with spam email.
Our company has created a system that could replace e-mail, that is secure by default, that uses a white-list system to eliminate spam, but apparently people are not interested in such a system.