Methods and apparatus, including computer systems and program products implementing a messaging protocol. The messaging protocol may be a messaging protocol for transporting a message across a messaging landscape in a collaborative network. Techniques include sending a message that is defined to include a structured message header with information related to at least one component from a set of components defined by a protocol, including protocol version information in a message such that a component of a messaging landscape can interpret the message based on the version information, defining a message as one of a class of messages, end-to-end acknowledgement for messages, and security for headers and payloads of messages.