The MAPS (Mail Abuse Prevention System) RBL (Real-time Black-hole List) is a list of networks, which are known to be friendly, or at least neutral, to spammers who use these networks either to originate or relay spam (unsolicited bulk email).
When enabled FTGate will validate any incoming server connections with the MAPS RBL. If the MAPS system reports that the server is blacklisted then no mail will be accepted from that site.
For more information see the MAPS RBL homepage: http://maps.vix.com/rbl
And for a full description of MAPS RBL see: http://maps.vix.com/rbl/rationale.html
The MAPS (Mail Abuse Prevention System) DUL (dial-up list) provides a list of ISP's IP addresses they have assigned to Dial-up accounts. The main use of this list is to assist in the prevention of mail system abuse by denying connections to any server using an IP address that appears on the MAPS DUL list, thus forcing Dial-up account users to route their mail through the ISP's mail systems.
For full information on MAPS DUL (Dial-Up List) see http://maps.vix.com/dul)