...
That's a personal proxy server.
Wiki Markup No Spam Today! POP3 Proxy for Workstations - \[http://www.nospamtoday.com/workstation\] - With just a few mouse-clicks, No Spam Today! is configured to run on any Windows 98SE/ME/2000/NT/XP/2003 system. No Spam Today! easily connects to any POP3 email client. It additionally provides a wizard to enable spam protection for all your Outlook POP3 mail accounts. \\Wiki Markup \[http://www.statalabs.com/products/saproxy/overview.php SAProxy\] by Bloomba is a Windows proxy server that's easy to set up and works quite well. It's $30. \\
Wiki Markup \[http://mcd.perlmonk.org/pop3proxy/ Pop3Proxy\] 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. \\
Wiki Markup \[http://sourceforge.net/projects/imapassassin ImapAssassin\] is a perl application which uses [SpamAssassin] to pre-filter an IMAP mailbox for spam, before you download it. \\
...