On 01/03/2016 04:52 PM, The Real Bev wrote:
This is new: Thunderbird seems to think that x-posted
messages/newsgroups reside on different servers and refuses to post.

How many servers do you have configured besides
news.eternal-september.org? Perhaps that news server has some
restriction regarding the number of newsgroups you could cross-post to?

The other issue could be that you haven't refreshed the available groups
on one of the configured news servers and it thinks that one of the
groups you're posting to doesn't exist for that server and it falls back
to a server that does have it. IME, the server it uses depends on what
you choose as the from field in the compose window. For example, I have
one for the news server I'm using to post this article and another one
for news.gmane.org.