http://www.rfc-editor.org/rfc/rfc5825.txt
RFC 5825: Displaying Downgraded Messages for Email Address Internationalization, K. Fujiwara, B. Leiba2010-04-01T23:00:00-00:00This document describes a method for displaying downgraded messages that originally contained internationalized email addresses or internationalized header fields. This document defines an Experimental Protocol for the Internet community.