ORBITrbl - Listing Criteria

Why my IP is Listed ?

Make sure your not sending SPAM or Bulk email to users with out there consent.
Make sure your NOT using a Dynamically Allocated IP. (See Wikipedia)
Make sure your NOT using a server that is hosting many domains; if any one of the users who use the server send spam from that server; IP may get listed.
Make sure your Servers/Network Computers (If NAT is used for clients) are not infected with Virus, Spambots & Adwares.