I don't think the owner of this group is sitting there approving and denying messages of people who have proven themselves not to be spammers; if he is then he needs a new hobby, like some of the owners and moderators of another group I'm on.
I'm not sure exactly what's happening for you but I find most of the the problems that make people think they are being blocked etc is actually Yahoo itself, I found that a lot of my posts when I replied by email were taking days to get through Yahoo's server,
sometime never making it through. If I posted directly from the groups page the messages went straight through.
All of these issues that Yahoo gives us is why many groups have left and gone to either social media (ugh!) or started their own forums on their own websites.