For a sender to be able to address the correct recipient unambiguously, all Access Points and associated recipients must recognise one another.
The Peppol Participant Identifier (Peppol Participant ID) is used in the Peppol network to clearly identify a participant. Recipients must be registered in an SMP (Server Metadata Publisher) server in order to even be discoverable in technical terms. Additional metadata for a participant, for example which document types the participant can accept and which Access Point they are connected to, is also saved in the SMP. The Participant Identifier for a sender is not registered in an SMP if the latter only wishes to send.