I have been looking at the symptom for over a month, but I have not found the cause yet. On my part, there is almost no change done to the server, and according to the log, it looks like it is deliverling the emails, whichi apparently is not true. Perharps it is now being caught by some kind of filtering rule that is in place at some ISP? Could you please write what provider you use for subscribing to the list?