[CentOS] A gmane mystery

I've been collecting redhat.fedora from gmane for several years,
but about a week ago I found that while I could read gmane newsgroups
I was unable to post to them - that is, my posts did not appear.

I was able to post to gmane.test, and could read these posts.
So I assume there is no problem with my From: or other headers.

I take it that the gmane.linux.centos.general is in fact
"mirroring" the mailman mailing list 
<http://lists.centos.org/mailman/listinfo/centos>
Assuming this is so, I don't know
whether the problem lies with the list or with the newsgroup?
I seem to be properly subscribed to the mailing list,
with my current email address.

Any enlightenment or advice gratefully received.

-- 
Timothy Murphy  
gayleard /at/ eircom.net
tel: +353-86-2336090, +353-1-2842366
School of Mathematics, Trinity College, Dublin