E3/Sentinel, a NewSpring Holdings company, is a mission-focused services and solutions company headquartered in McLean, VA. S ... ince E3 Federal Solutions and The Sentinel Company combined forces in 2018, E3/Sentinel works as a combined entity to draw upon their long histories of consistent growth and high performance in the federal services market. The company’s services and solutions are designed, tailored, and executed based on the experience both organizations bring from helping their Homeland Security, Defense, Intelligence, and Federal Civilian customers solve complex problems. Learn more at www.e3sentinel.com. read more