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 software 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.