Cryptographically protected email aims in hiding and protecting. Extending this to an uppermost extend also for trace headers, and/or the transport layer, so that only directly involved hops, which need to have a notion to "know", the sending system and/or the receiving system thus, can interpret certain header information, can be important. This document ensures that only the receiving system, in its desire to prevent email loops, can interpret the real content of the delivery notice header.