I have reviewed this document as part of the security directorate's ongoing effort to review all IETF documents being processed by the IESG.  These comments were written primarily for the benefit of the security area directors. Document editors and WG chairs should treat these comments just like any other last call comments. This standards-track document suggests a method for internationalized mail servers to "downgrade" internationalized messages to standard/basic mail clients.   The document is clearly written and the Security Consideration section does discuss the potential issues I could think of. I have no further comments. -- Magnus