Find sensitive data types in Outlook mailboxes

Hi GI472,  

Your use case is in other words about data discovery.

Content Explorer is good place to look for such content but you have to parse the data to be able to read it correctly.

https://learn.microsoft.com/en-us/microsoft-365/compliance/data-classification-content-explorer?view=o365-worldwide

You can try to extract the data and visualize it using Power BI for example similar to what was done in this reference Microsoft 365 Compliance audit log activities via O365 Management API - Part 2 - Microsoft Community Hub

As for confidence level indicated in the content explorer it is based on confidence level of the SITs and this can be changed https://learn.microsoft.com/en-us/microsoft-365/compliance/data-classification-increase-accuracy?view=o365-worldwide

If you need to look from now on, I would suggest to add some policies to inspect content using one of multiple options available. Such as a file policy within Microsoft Defender for Cloud Apps with filter App=ExchangeOnline to discover specific SITs or Trainable Classifiers using content inspection.

https://learn.microsoft.com/en-us/defender-cloud-apps/data-protection-policies

https://learn.microsoft.com/en-us/defender-cloud-apps/dcs-inspection

Here you have to be careful since you are looking at real user data and you may have legal obligations for your actions.

Thank you and kind regards