/$LISTNAME/$MESSAGE_ID -> 301 to /$LISTNAME/$MESSAGE_ID
/$LISTNAME/$MESSAGE_ID/raw -> raw mbox
/$LISTNAME/$MESSAGE_ID/f/ -> HTML content (full quotes)
+/$LISTNAME/$MESSAGE_ID/R/ -> HTML reply instructions
### Legacy endpoints (may be ambiguous given Message-IDs with similar suffixes)
/$LISTNAME/m/$MESSAGE_ID/ -> 301 to /$LISTNAME/$MESSAGE_ID/