As far as I was able to find out it is impossible to block them permanently,
because the hackers have a way to get around the block. I had the same
question several months ago, and I asked a technician about it and this is
what he told me. It is not that the message is not being blocked, but they
manage to somehow hack in to the system. I know that this is not what you
wanted to hear, but maybe Microsoft can come up with a super solution in the
near future. I have a spam program and all the junk e-mail go automatic there
so it is easier to get rid of them. You can have it for free,
http://www.openfieldsoftware.com/ .
Sol