بسم الله الرحمن الرحيم
(1) Such a person is also Muslim.
(2) But he is transgressor and sinner. He shall be given bath after his death like any other Muslim and wrapped in coffin and his janazah salah shall also be offered and he shall be buried in the graveyard of Muslims as per Islamic rites. He shall be treated like Muslim. Such a person should be preached and informed of religious matters time and again. Efforts should also be made to send him in tablighi jamah.
Allah knows Best!
Darul Uloom Deoband
This answer was collected from the official ifta website of Darul Uloom Deoband in India.