There was a big Nestorian Christian population in Najran (historically and culturally Yemeni). The brutal persecution of those Christians by the Jewish Himyarites was the reason the Axumites conquered Yemen. Surprisingly the population of Najran is Ismaili now lolThere was a Christian minority in Arabia, but most Arabs were Pagans and there was also a fairly large Jewish presence in Arabia back then [Yemeni Jews were the last remnants of Jewry in Arabia before they were taken to Israel].