Mandatory
This field specifies the reference assigned by the Sender to unambiguously identify the message.
This field must not start or end with a slash '/' and must not contain two consecutive slashes '//' (Error code(s): T26).
The reference assigned to a reset/advice is used for cross-referencing purposes in subsequent messages, such as following reset/advice and statement messages as well as queries. It is therefore essential for the identification of the original message sent that this reference be unique.