Maintaining the Users
Users to be propagated must be maintained in the messaging components with the same name as in the sender system. For security reasons, we recommend that you create these users as users of type system and not as dialog users. These users must be assigned the role SAP_XI_APPL_SERV_USER.

If you use access control lists (ACLs) for messages with specified sender systems or interfaces, these ACLs must include propagated application users if principal propagation is applied.
More information:
Service Users for
Message Exchange.