This Technical Report consists of three parts.The first part defines, describes and explains basic concepts typical to all mail communication systems such as; domains, parties, agents and their role in the system, physical and informational objects, processes, interfaces and relationships. The first part does not cover more detailed technical aspects of the main concepts such as:- a detailed description of mail units and sets, their attributes and methods of collection/capture of their values; - applications describing specific use of the information describing basic objects by mailers, postal operators and recipients;- data elements, data constructs and message descriptions;- communication protocols and infrastructure for message transport including transport of messages through a print-scan channel (or paper channel);- message security issues related to individual messages: confidentiality and integrity of data, authentication and non-repudiation; - printing symbology, physical placement of data elements and symbols, their orientation and dimensions, and inks and print quality.The second part of this Technical Report defines the necessary and sufficient concepts for customer directed information that can be captured by post and made accessible to customers using post mailer interface. This report explains and describes relationships between these concepts. This report provides a comprehensive list of mail unit attributes that are involved in forming observations and events significant for postal customers. This report describes a methodology suitable for the selection of observation points within postal domain process where information collected in observations is most useful for customers. The report does not cover:- applications describing the use of collected event information; - messages and protocols;- communication infrastructure. The third part of this Technical Report describes:- a list of specific events knowledge of which is valuable to postal customers (mail senders and recipients) and could be made available to such customers;- underlying mail unit attributes that form corresponding observations;- data construct supporting practical access to information collected within postal domain about events, underlying observations and expectations, and in particular information about events, observations and expectations that are valuable to postal customers. This Technical Report also provides an example of application that demonstrates the use of specific events and data constructs. This Technical Report makes use of XML schema in describing relevant data constructs. Actual communication messages can be built from data constructs described in this report. However, this report does not specify the structure of specific messages, nor does it preclude using mechanisms other than XML schema to describe data constructs.