I will discuss the structure of the Nelson-Barr approach to the strong CP Problem, and argue that these solutions can be naturally embedded into E6 Grand-Unified Theories, since the E6 fundamental contains all necessary fermions.The main benefit of the unified structure is the predictivity in the SM fermion sector, and a perfect fit to all SM observables can be obtained despite being over-constrained. Definite predictions are made for the neutrino sector, with a Dirac CP phase that is correlated to the CKM phase, allowing to test this model in the near future.