Spam blockers

[DomainEmpire.com]

Hi all,

We're looking for a free spam blocker where nobody can reach us without having clicked a link first, to be entered in our "white list", something as www.mailblocks.com but free ...

mailblocks is really very cheap but we need to use it on a couple of mailboxes with no real importance, just to avoid spammers continues to bombard them every damn day

I see that my friend Andrew (whois-search) has already posted a similar thread but what I need is a bit different; anyway, I'm thinking to try spamassassin on our main accounts ;-)