-applies one transformation unconditionally: it removes an extraneous
-trailing semicolon from the parameter lists of MIME header fields.
+applies two transformations unconditionally.
+The first removes an extraneous trailing semicolon from the parameter
+lists of MIME header field values.
+The second replaces RFC 2047 encoding with RFC 2231 encoding of name
+and filename parameters in Content-Type and Content-Disposition header
+field values, respectively.