“Failed to Synchronize Item Changes in Folder” While Processing Public Folders in Veeam for Microsoft 365

When backing up public folders in Veeam Backup for Microsoft 365, you might encounter the frustrating error:

Processing mailbox PublicFolderMailbox@xxxxxxxx.onmicrosoft.com failed with error:
Failed to synchronize item changes in folder: FOLDERNAME..
Access is denied. Check credentials and try again., ICS synchronization failed.

This issue can cause public folder backups to complete with warnings or fail altogether, jeopardizing backup consistency for shared organizational data.

Possible causes include the following:

• Public folders are not located under the IPM_SUBTREE folder.
• The Veeam service account lacks permission to access public folders.

Solution

Check the Location of Public Folders

Veeam backs up only the IPM_SUBTREE branch. If public folders are located outside IPM_SUBTREE, Veeam will return the warning.

Assign Service Account Permissions to Public Folders

You can run the following PowerShell script to assign ownership to the Veeam service account for all public folders. (If you are unsure what service account is used for backups, please contact our support team.)

*Please note that the script will not work if the service account has a Shared mailbox. Shared mailboxes are not supported for public folder ownership.

# Set $user to the Veeam Backup for Microsoft 365 Service Account
$user = "YourVeeamServiceAccount"

# Connect to Exchange Online
Connect-ExchangeOnline

# Get all public folders recursively
$folders = Get-PublicFolder -Recurse

# Loop through each public folder and add the specified user with Owner access rights
foreach ($folder in $folders) {
    Add-PublicFolderClientPermission -Identity $folder.Identity -User $user -AccessRights Owner
}

# Disconnect from Exchange Online without confirmation prompt
Disconnect-ExchangeOnline -Confirm:$false

The “Failed to synchronize item changes in folder” error during public folder processing in Veeam typically points to issues with permissions or connectivity. By verifying the service account’s access rights and public folders’ location, you can resolve this error and maintain reliable backups.

For any additional information or assistance, please contact our support team at support@managecast.com