Such report can only be generated by EWS-based script (or a Graph-based one if using Exchange Online). Here's a sample one to get you started: https://gsexdev.blogspot.com/2013/09/exchange-attachment-statistics.html
tracking largest attachments and number of attachments
Abdulbari M. Alfatani
20
Reputation points
Dear ,
I'm trying to generate report that track number of attachments for all users.
for instance, the report should show the attachment size per user.
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