MFT 12c Transfer notification: one poll per email

I want to configure, one email which should include all successfully transferred files at source at a given time.

We have tried, 1.Post Processing Actions --> Transfer Notification--> by adding/updating contacts

2. Tried through custom call out as post processing action by overriding process()

But we are receiving emails per each file/each instance. But we want to configure, one email which should include all successfully transferred files at source at a given time.

Our expectation was to, In one email notification include all file names processed/picked from source at a scheduled particular time need to notify.