MegaRBL is a DNS based blacklist. It's a French website whose goal is to offer its service for free to filter the spam that can be received every day. It proposes an RBL (Real-time Blackhole List) that anyone can use to protect themselves from unsolicited e-mail.
MegaRBL maintain a listing of known spammers and reports them to their Internet Service Providers, helping them to take the appropriate actions.
It is composed of people who are not paid for what they're doing, and the website doesn't receive any subvention or money from internet industry. In order to avoid abusive reports (Competitors, false positive, etc...) only MegaRBL team can add IPs to the list.
If an IP is blacklisted on MegaRBL, that means that an unsolicited e-mail has been receive in one of the team's spamtrap. MegaRBL does not take reports and only function with spamtrap and honeypot in order to avoid any abuse. A server running as an open relay that sends spam in one of the spamtrap will also result in a listing on the RBL. It's important to note that any mail receive in one of those trap will be unsolicited and therefore the IP listed.
However, MegaRBL does not list dynamic IP address as it will not be of any help to prevent further spam. It doesn't list ranges of IP addresses either.
The primary and only DNS zone for MegaRBL is rbl.megarbl.net. When you query the zone and an IP is listed it will return 127.0.0.2. If you want to use the zone, the configuration is like any other DNS blacklist, or explained on the FAQ of MegaRBL.net.
In order to remove an IP from the blacklist you must create an account (free membership). You must then fill a form explaining which actions have been taken to stop the spam sending. The IP is then removed from the blacklist within an hour.
However, if an IP address is blacklisted several times and has already been unblackisted, the process may take more time, as there will be manual verifications.