fix typo in reference to RFC 3464 DSN MIME type

Doc/lib/emailparser.tex

@@ -144,7 +144,7 @@ Here are some notes on the parsing semantics:
       \class{Message} subparts.
 
 \item Most messages with a content type of \mimetype{message/*}
-      (e.g. \mimetype{message/deliver-status} and
+      (e.g. \mimetype{message/delivery-status} and
       \mimetype{message/rfc822}) will also be parsed as container
       object containing a list payload of length 1.  Their
       \method{is_multipart()} method will return \code{True}.  The