EBS workflow Inbound mails history?

Hello,

We need to find the list of actively used EBS workflow item types that generate outbound emails that require users' replies (such as expense report approval request emails that users can reply with either approval or rejection).

When users send replies to EBS, the inbound email records are recorded in WF_NOTIFICATION_IN. However, as they are processed, they are deleted from WF_NOTIFICATION_IN (unlike the outbound email records that persist in WF_NOTIFICATIONS until data purge). So we cannot see the historical data of all the user reply email records. Is there some way to find them out?