Assistance with Identifying Usernames in Exchange/Outlook Reports

Hi @Alvin Dela Cruz

Thank you for posting your question in Microsoft Q&A. 

We understand you're considering updating the user identifier in the usage report from a long alphanumeric string to more recognizable formats such as account names or email addresses. We're happy to assist with this. 

The use of long alphanumeric strings in the usage report is a default behavior designed to hide user, group, or site details for privacy reasons. 

The string you're seeing is the user's Mailbox GUID (Globally Unique Identifier), also known as the ExchangeGuid. Microsoft 365 and Exchange use this GUID as a permanent, immutable identifier for a mailbox. Unlike an email address or User Principal Name (UPN), which can be changed, the Mailbox GUID remains constant and ensures a stable reference to the mailbox object. 

You can revert this change for your tenant and show identifiable user, group, and site information if your organization's privacy practices allow it. 

• In the admin center, go to the Settings > Org Settings page. 
• Select the Services tab, then select Reports. 
• In the Reports panel, select the checkbox next to Display Concealed user, group, and site names in all reports. 
• Select Save. 

You can refer: Microsoft 365 admin center activity reports - Microsoft 365 admin | Microsoft Learn 

If you have any additional concern, feel free to comment below. I be more than happy to assist. 

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