In the E-3, additional armour was fitted to protect crew. Armed with forward firing 20 mm MG FF cannon and seven MG 15 machine guns. (Despite the large number of machine guns, the defensive weight of fire was light, with five of the gimbal mounted machine guns to be operated by the radio-operator, who could only use one at a time).

The E-4 was similar to the E-2, which it replaced in production, but with the dive brakes removed. It was fitted with Kuto-Nase barrage-balloon cable cutters in the leading edge of the wings. 258 E-3 and E-4 were built. The E-4 was identical to the E-2, with the exception of the heavy MG FF in the nose. Five of the six positions were flexible, with only one fixed gun; the MG FF installed along the floor, just off centre. The cannon in the nose could be moved. Both were powered by BMW 801L engines.

The E-5 was a modified version of E-4 for anti-shipping operations. It was fitted with a bomb carrier for a Henschel Hs 293 glide bomb or a drop tank under each of the outer wings, and carried the appropriate Kehl series radio guidance and control transmitter system for the missile. It was usually operated with a missile under the starboard wing and a drop tank under the port wing. Sixty-seven were new-built with additional 34 converted from E-4 airframes.

Testing with glide bombs was halted as the electrics were too sensitive to moisture, rockets prone to icing and the radio valves in the control units (in the aircraft) were disrupted by vibrations. By May 1942, hit rates were just 50 percent. In April 1942, the first E-5 reached the test centres at Peenemunde. Various test were made with aircraft with anywhere from 15.4 and 16.5 tonnes in all up weight. Often these tests were made to assess flight characteristics when carrying glide bombs such as the Hs 293. The E-5 was given heating units to keep the cold form the heat-sensitive glid bombs' electrics. With external ETCs, but without Glide bombs and auxiliary fuel tanks, the E-5 could attain of a speed of 480 kph at 5,000 m. With two external stores, its speed was reduced to 445 kph and its weight, including 4,300 litres of fuel, was 16.85 tonnes.

The Do 217 E-2/U1 was used as a E-5 prototype. Whether a E series Do 217 ever launched a Hs 294 glide bomb is unclear. The only known fact is that a Do 217 flew a Hs 294 to Berlin-Schonefeld in May 1943. The first launch of the missile was done from a Messerschmitt Bf 110, and thereafter was taken over by the Heinkel He 177 equipped with the FuG 203 Kehl transmitter to control the missile. Only the Do 217, He 177 and Focke Wulf Fw 200 could carry a Hs 293/4 or Fritz X missile.

Sources:
Gunston, Bill - The Encyclodepia of the Worlds Combat aircraft, 1976, Chartwell Books, Inc., New York
Brown, Eric, Captain - Wings of the Luftwaffe, 1979, Airlife Publishing Ltd., Shrewsbury
Gunston, Bill & Wood, Tony - Hitler's Luftwaffe, 1977, Salamander Books Ltd., London
Donald, David - The Complete Encyclopedia Of World Aircraft, 1997, Brown Packaging Books Ltd., London
Wikipedia - Dornier Do 217