Yet the Mormon baptism is not accepted by the majority of Christian churches.
... and baptism by any church other than theirs is rejected by Mormons, otherwise the controversial practice of baptism for the dead would not be deemed necessary for those who had been baptised and died in Christ. I don’t know the state of the souls of many of my paternal male ancestors, but they have been baptised after death by Mormons. Much of it is wrong, wrong name, wrong date of birth, wrong date of death, wrong geographic location. This renders even the value of the LDS library as a geneological resource suspect. I don’t doubt they do it in all sincerity, but the practice implies negative things to those outside their church.