We publish a Terms of Service as part of our signup process, and nothing you see on this page will supersede that Terms of Service, but you should be aware of the following things that will influence whether or not your application is accepted.
Clear Ownership of the IP - Since our FBL is keyed to the sending IP, data we present will be about all mail from the IP, not just mail from a given domain. Therefore, the enrolling party must clearly be the one responsible for all mail from the IP. We'll most likely try to verify ownership through reverse DNS for the IPs and WHOIS information for the IPs and/or domains involved; if it's not immediately obvious to us that the party applying for enrollment is responsible for the IP, then chances are very good that the application will be rejected.
Generic or Non-Existent PTR Records - PTR records (a.k.a. reverse DNS records) go a long way toward establishing the party responsible for an IP address, and they're required to get any mail accepted here. IPs with no resolvable PTR record (NXDOMAIN or SERVFAIL) or with a generic PTR record (one that just restates the IP address in some fashion) will be rejected on any applications for our FBL.
IP Being on a Blacklist - We use several third party black lists to control connections to our inbound mail servers; if an IP in an application is on any of them, you should request to be removed from these list but it will not prevent you from enrolling for an FBL.