Get-MgUserMailFolderMessageCount: A Comprehensive Guide

The Get-MgUserMailFolderMessageCount cmdlet is part of the Microsoft Graph PowerShell module, specifically within the Microsoft.Graph.Mail submodule. This cmdlet allows administrators to retrieve the count of messages in a specific mail folder of a user's mailbox. It's particularly useful for monitoring mailbox usage, auditing, and reporting purposes.

Cmdlet Syntax

Get-MgUserMailFolderMessageCount -UserId <String> -MailFolderId <String> [-Filter <String>] [-Search <String>]

• -UserId: Specifies the unique identifier (GUID) or User Principal Name (UPN) of the user.
• -MailFolderId: Specifies the unique identifier of the mail folder.
• -Filter: Filters items by property values (optional).
• -Search: Searches items by search phrases (optional).

Usage Examples

Example 1: Retrieve the Total Message Count in a Specific Folder

$userId = "user@domain.com"
$mailFolderId = "AAMkAGI2TAAA="
Get-MgUserMailFolderMessageCount -UserId $userId -MailFolderId $mailFolderId

This command retrieves the total number of messages in the specified mail folder for the user.

Example 2: Retrieve the Count of Unread Messages in a Specific Folder

$userId = "user@domain.com"
$mailFolderId = "AAMkAGI2TAAA="
Get-MgUserMailFolderMessageCount -UserId $userId -MailFolderId $mailFolderId -Filter "isRead eq false"

This command retrieves the count of unread messages in the specified mail folder by applying a filter.

Cmdlet Tips

• Obtaining Mail Folder IDs: To execute this cmdlet, you need the MailFolderId. You can obtain it using the Get-MgUserMailFolder cmdlet:

$userId = "user@domain.com"
Get-MgUserMailFolder -UserId $userId | Select-Object DisplayName, Id

Since the IDs are lengthy, it's advisable to export them for reference:

Get-MgUserMailFolder -UserId $userId | Select-Object DisplayName, Id | Export-Csv -Path "C:\Path\To\MailFolders.csv" -NoTypeInformation

• Filtering Results: Use the -Filter parameter to narrow down results based on specific criteria, such as retrieving only unread messages.
• Search Functionality: The -Search parameter allows you to search for messages containing specific keywords.

Use Cases

• Mailbox Auditing: Monitor the number of messages in specific folders to ensure compliance with organizational policies.
• Storage Management: Identify folders with large numbers of messages to manage storage effectively.
• User Support: Assist users by providing insights into their mailbox usage, such as identifying folders with unread messages.

Possible Errors & Solutions

Error	Cause	Solution
Resource not found	The specified mail folder does not exist.	Verify the MailFolderId parameter using Get-MgUserMailFolder.
Access Denied	Insufficient permissions to access the user's mail folder.	Ensure the executing account has Mail.Read permissions.
Invalid UserId	The -UserId parameter is incorrect or the user does not exist.	Double-check the User Principal Name (UPN) or user ID. Use the Get-MgUser cmdlet to verify the user information.

Conclusion

The Get-MgUserMailFolderMessageCount cmdlet is a valuable tool for administrators to monitor and manage user mailboxes within Microsoft 365. By understanding its syntax, usage, and potential errors, administrators can effectively leverage this cmdlet for various tasks, including auditing, storage management, and user support. Always ensure you have the necessary permissions and verify parameters to avoid common errors.