This paper proposes and investigates a novel electro-magnetic vibration energy harvester using ortho-planar springs. Addressing the limited output power of previously reported designs, the proposed harvester targets milliwatt level power outputs to be relevant for practical sensing and IoT applications. The proposed design employs an optimized pickup unit with Halbach array configuration and an optimized ortho-planar spring, which are integrated in a 3D-printed housing. During experimental evaluations, the harvester demonstrates an output power of up to 5.26mW and a normalized power density of 133.05 μW/(cm3∗g2), exceeding the performance of previously reported harvesters with ortho-planar springs. Moreover, exploiting the versatility of ortho-planar spring designs, it is shown that the harvester's frequency response can easily be adjusted to different application conditions.