My ex and her now 27 year old daughter have been both accusing me of indecent assault or sexual assault with the daughter when she was a child, some 18 years ago since I saw her last or last had any contact with her. I have been receiving threatening emails and have been told by people who know both of us that this is what they are saying. So the 27 year old is making the claims and the mother is spreading them. What should I do? Is it defamation?