There's nothing in the code to cause that so I don't know what's happened. I've corrected it and may re-send the letter later.
# I don't think the latest muse-letter actually went out properly. I just checked the database and all the commas had been somehow removed from the list of addresses. That's obviously not going to work.
There's a bug somewhere when someone unsubscribes from the daily emails or muse-letter, it's this glitch which removes the commas from the list of email addresses. I received an unsub mail with no details so suspected something was wrong, sure enough when I looked in the database the same thing had happened. Looks like I'll need to dig in to find out what's happening.