Answer
(Fatwa: 350/350/M=1432)
The Ibadi sect (اباضی) exists in Muscat and ‘Ibadi (عبادی) might be its misspelt name. We do not have complete knowledge about the beliefs of Ibadi sect. However, this sect is attributed to Abdullah ibn Ibadh and it is a branch of Khawarij sect. Their beliefs are found in the books. If this sect (Ibadiah) is the same and it holds the same beliefs, then salah should not be offered behind them, it will not be valid. (Ahsan al-Fatawa 1/198)
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband