One workaround to do force deletion is
http://<pihost>:<port>/MessagingSystem/archiving/reorgdb.jsp
Delete for messages over Retention Policy :
SAP XI AF CORE --> idmapRemover.checkInterval = Number of messages
The default persist duration is 30 days and it can be changed with the persistDuration properties of the J2EE service: "SAP XI Adapter: XI"
table XI_AF_MSG_AUDIT
Regards,
Abhi