THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
You can run a small proxy application on your client computer that will connect to your mail server, get the email, run SpamAssassin on it, then deliver to your email client.
That's a proxy server.
SAProxy by Bloomba is a Windows proxy server that's easy to set up and works quite well. It's $30.
Pop3Proxy (http://mcd.perlmonk.org/pop3proxy/) is a open source (perl) proxy server that seems to mostly work for Windows machines. Setting it up is *not* point-and-click easy, however.
The link is dead - no idea where it has gone..... 