Why Vet new Clients? According to MAAWG: "ESPs take on significant risk every time a new customer sends email. A bad client can undermine the sending reputation for the ESP’s other clients as well as inflict abuse at recipient domains. When proper pre-send vetting is performed, ESPs can preempt damage caused by bad clients to both recipient domains and to their own sending reputation. " If you are building a client vetting program, the following is a list of some recommended resources, courtsey of OI member Andrew Bonar: