@achso@mastodon.social LOL, I had a hunch, and it was the right one.

Mr Furrow responded to my letter with promptness, thanked me for mine, and confirmed it was because our instance allows Federation with one in particular that he objects to; and to protect their users, this ban was put in place.

His suggestion, which I will bring to our admin staff is that we dissociate from that particular domain, if we want to federate with his.