Unable to link (add) user id in yahoo group?

Question

I want to link (add members) to one of the yahoo group, but it denies and prompts that user cannot be added, but it allows the other users email id's. But I do not know what is the problem

Answer 1

it means those people selected a setting which makes it so you cant add them as members, it's a neat little feature to prevent abuse of the adding of members without permissions, which is a violation of Yahoo TOS.