Generate a report of emails with attachments over a specific size

[JMcElvoy77]

I have a customer that has been asked by an auditor to know when their users send emails with attachments over a specific size.  They're on M365 E3 today.  Can we generate a report that will capture when emails are sent outside their network over 10Mb?  

[#2]

How frequently is the Auditor wanting this information?

I've not looked at reports, but you can setup a transport rule to notify someone whenever a file with an attachment over a specified size is sent.

[#3]

The auditor is requiring them to have this in-place permanently. Thanks for the info. I was able to find an article discussing setting up mail flow rules for this.