 This is for several reasons, including problems related to the Y2K bug.In some cases, the original authors have left the BBS or shareware community, and the software, much of which was closed source, has been rendered abandonware.Several DOS-based legacy FidoNet Mailers such as FrontDoor, Intermail, MainDoor and D'Bridge from the early 1990s can still be run today under Windows without a modem, by using the freeware NetFoss Telnet FOSSIL driver, and by using a Virtual Modem such as NetSerial.