/$INBOX/$MESSAGE_ID -> 301 to /$INBOX/$MESSAGE_ID/
/$INBOX/$MESSAGE_ID/raw -> raw mbox
-/$INBOX/$MESSAGE_ID/R/ -> HTML reply instructions
+/$INBOX/$MESSAGE_ID/#R -> HTML reply instructions
# Covering up a pre-1.0 design mistake:
/$INBOX/$MESSAGE_ID/f/ -> 301 to /$INBOX/$MESSAGE_ID/