To search for email which has large attachments, in Outlook:
- In your list of folders, scroll down and right click on “Search Folders“
- Click on “New Search Folder“
- Then select “Large Mail”
- Click the “Choose” button and change the number to “10,000 KB“
- And click “OK“
- Outlook will now search all email and display a list that has attachments totaling more than 10mb per message.