Public Folder Backup Hangs
Challenge
An Exchange backup job that contains a public folder mailbox runs in an endless cycle, continuously getting changed items from one of the public folders. In the job logs, you can see multiple entries in the following format:
Changed items: 0, deleted items: 0, read state changes: 100 Processing mailbox: <mailbox_name>... Syncing folder items: <folder_name>... Sync time: <time>
Cause
This issue was investigated and determined to be caused by a public folder with the parameter PerUserReadStateEnabled set to True.
Solution
To prevent the backup from looping while processing a public folder, that folder must have the ‘PerUserReadStateEnabled’ parameter set to ‘False’ in M365.
Important Note
When PerUserReadStateEnabled is set to False on a public folder, all users with access to that folder will observe a unified Read/Unread status for messages within that folder. For detailed information, review this Microsoft article.
Set Parameter Using PowerShell Script
To help expedite the resolution of this issue, a PowerShell script has been developed to set the PerUserReadStateEnabled parameter to False for the problematic public folder(s).
Script Requirements
- Before running the script, you must update the following variable:
- $folders (line 17) — As shown in the script's example folder values, list the problematic public folder in double quotes separated by a comma.
Note: If the folder names are unknown or there are many folders, the $folders variable may be set to '$folders = $null', and the script will set the parameter PerUserReadStateEnabled to false for all public folder mailboxes.
- $folders (line 17) — As shown in the script's example folder values, list the problematic public folder in double quotes separated by a comma.
- This script uses the ExchangeOnlineManagement module.
If the ExchangeOnlineManagement module is not installed or fails to be imported when the script is run, uncomment "Install-Module ExchangeOnlineManagement" (on line 15) and run the script again to have the script install the ExchangeOnlineManagement module.
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