Question:
If my front door has a screen door in front of it, where does the mezuza go? Within a tefach of the screen door or within a tefach of the main door?
Answer:
On the assumption is that the screen door is very close to the regular door, both doors need the same mezuza. Ideally the mezuza should be placed inside the doorway, in the first tefach closest to the outside, and not in the front of the doorway. Therefore it should be placed in the doorway of the main door.
Best wishes
Sources:
Rema Y:D 289-2
