Software company MailFrontier said Monday that it raised $5 million from a group of investors and launched a test version of its anti-spam technology, the latest in a string of new products aimed at fighting unwanted e-mail. The Palo Alto, Calif.-based company raised a first round of funding from investors led by Draper Fisher Jurvetson and New Enterprise Associates. Simultaneously, the company introduced Matador, free that helps consumers block junk mail from their in-boxes. The technology works by using a combination of spam-blocking techniques, including collaborative filtering by users of the system and white lists, or a list of people the recipient agrees to hear from. The software works for users of Microsoft Outlook, running on Windows 98 and higher.