Santa Cruz, Calif.-based Open Field Software began shipping its Ella e-mail application for Microsoft Outlook users, the start-up said Wednesday. The program learns how people prefer to organize their messages based on behavior and then can automatically sort them into three customizable categories such as "in-box," "later" and "spam." The $30 program supports Outlook XP or 2000 when run on Windows XP, 2000, 98 or ME operating systems. The company is beta testing an IMAP version. A 15-day trial version is available for free.