I've just updated the list settings in light of some recent spam.
Messages will be held for moderation. This is not great, but it will help us to keep out obvious spam. When someone posts for the first time, we'll either mark them as "whitelisted" so that all subsequent messages do *not* get moderated and just go right through.
So, those of you who have been on the list for a while will see your next message get held, but I'll keep on top of that to make sure you're then whitelisted.
Sorry for the inconvenience.