I have been testing the send messages feature in admin and I couldn't get the send to "All Customers" to work. I then realised that this selection is for those members that have signed up to the newsletter.
Should there be a separate selection for send to "all newsletters". I see there is a line in the language file "text_all_newsletters" but it's not in the drop down menu in admin messages.
When I try and archive the messages I see "Message has been moved to archive" but they are not transferred to the archive folder. Also I can't see how to delete unwanted messages.