We use file name suffixes on all of these (except /) so URLs may easily
cached/memoized using a static file server.
+Encoding notes
+--------------
+
+Raw HTML and XML should only contain us-ascii characters which render
+to UTF-8.
+
+Plain text (raw message) endpoints display in the original encoding(s)
+of the original email.
+
Guidelines for using limited HTML
---------------------------------
We mainly use HTML for linking pages together with <a>.