qmail has quietly become one of the most widely used applications on the Internet today. It's powerful enough to handle mail for systems with millions of users--Like Yahoo Mail and Hotmail, while remaining compact and manageable enough for the smallest Unix- and Linux-based PC systems. Its component design makes it easy to extend and customize while keeping its key functions secure, so it's no wonder that adoption of qmail continues at a rapid pace.The downside? Apparently none. Except that qmail's unique design can be disorienting to those familiar with other popular MTAs (Mail Transfer...