/$LISTNAME/m/$MESSAGE_ID -> 301 to .html version
/$LISTNAME/f/$MESSAGE_ID.html -> HTML content (full quotes)
/$LISTNAME/f/$MESSAGE_ID -> 301 to .html version
/$LISTNAME/m/$MESSAGE_ID -> 301 to .html version
/$LISTNAME/f/$MESSAGE_ID.html -> HTML content (full quotes)
/$LISTNAME/f/$MESSAGE_ID -> 301 to .html version