Public Folders work fine. But when it comes to migrate them to an Office 365 tenant, it may be a bit chaotic. Issues may arise, especially when you have large Public Folders.
In case of a hybrid setup – be it Exchange Server 2010, 2013, 2016 or 2019, following are the steps to migrate the Public Folders:
- Download the Migration Scripts from Microsoft to run on the on-premises server.
- Prepare for the migration by checking that there are no orphaned Public Folder objects and confirming their SMTP email address while making sure that there are no duplicates.
- Generate CSV Files for mapping local Public Folders to online Public Folders.
- Create Public Folder Mailboxes in Exchange Online.
- Start the migration request by using the downloaded scripts.
- Lockdown the Public Folder on the legacy Exchange Server so that no changes are done on them. Here is where downtime starts. And you need exclusivity of the folders to start off the migration.
- Finalize the Public Folder migration to kick off the migration of data and synchronization of file between local and the online folders.
However, sometimes, at the last step you might end up facing the below given error.
A Corrupted item was encountered: Folder ACL
However, you can avoid this error by following the fixes discussed below or using an Exchange Migration tool, such as Stellar Migrator for Exchange. The software lets you migrate the mailboxes and Public Folders from Exchange Server to Office 365 in a few clicks.
How to Fix the ‘A Corrupted item was encountered: Folder ACL’ Error?
Troubleshooting this error can be of a hassle. Although the process is supported by Microsoft, it involves a good number of scripts and depends on several factors of the Exchange Server, such as it is healthy and running well. Also, there are too many points of failure which could take a while to understand where the issue is.
When migrating Public Folders to Office 365, you must also take the limits into consideration, as given below.
- Maximum Public Folders – 250,000
- Maximum sub-folders in a Public Folder – 10,000
- Maximum items per folder – 1,000,000
- Maximum Public Folder mailboxes – 1,000
You would also need to consider the size of the items. An item cannot be larger than 49 MB. During migration, large items may be skipped or the whole process may stop.
Public Folders are known to give issues, especially when they’re large-sized. Although they are still highly used, it seems that Microsoft is phasing them out when it introduced Shared Mailboxes and Microsoft Teams/ Groups. This is great, but you will end up with the dilemma on how to export the Public Folder to a PST file.
One of the solutions would be to export the Public Folder to PST and import it directly into Office 365 by using the Blob Storage for import and the XML file to start the migration. Unfortunately, you cannot use the New-MailboxExportRequest cmdlet to export Public Folder to PST. Instead, you can use the Outlook to export Public Folder to PST. For this, you need to have a dedicated resource with Microsoft Office installed.
However, there are some limitations when it comes to exporting Public Folder to PST by using Outlook.
- There is a size limit of 50 GB.
- For large Public Folders, it is a messy situation as Outlook would not be able to handle large PST files.
- There is no continuity if the process stops or Outlook crashes.
- It will take ages to finish.
- The Public Folder must be online.
- Cannot export more than one Public Folder at once.
- No option to export selectively.
- It’s difficult to troubleshoot, if any issues arise during export.
- Too much loose ends.
An Alternative Solution
So, is there an alternative to avoid these problems? The alternative is a small but very powerful Exchange Migration tool called Stellar Migrator for Exchange. With this software, you can easily migrate mailboxes, Public Folders, and archive mailboxes directly between on-premises Exchange Servers or from Exchange to Office 365 (Microsoft 365) with ease.
You can perform cross-forest, cross-domain, and hybrid migrations without downtime or data loss. The tool allows you to migrate all or selected mailboxes, apply filters, and monitor the migration progress in real time.
Unlike manual methods, Stellar Migrator for Exchange simplifies the entire migration process, no complex PowerShell scripting, and no mailbox size limitations. It’s the ideal solution to ensure a fast, secure, and hassle-free Exchange migration.
