A doorway with lintel and 2 sides like a regular doorway but it does not have a door, is a mezuzah need and if so does it require a BRACHA?
There is controversy about this among the rishonim, therefore we put up a mezuza, but without a bracha. It should be noted that due to the above controversy, if you are intending to put a door on that doorpost, it should preferably done before putting up the mezuza there. Otherwise it is like putting up the mezuza when the door was exempt from mezuza, which is “taaseh v’lo min ha’asui” according to the opinion that it is exempt from mezuza. If you already put up the mezuza, it should be taken down before placing the door in its place and reaffixed again afterwards without a bracha.
Rambam HIlchos Mezuza 6-1, Raavad on Rambam, Shulchan Aruch Y:D 186-15, Shach ibid 25, Chayei Adam 15-9, Aruch Hashuchan Y:D 186-24, Chovas Hador 7-17.