Migrate Exchange Public Folders to Office 365 Groups Using MRS

Anuraag Singh | December 20th, 2018 | Updates

Exchange users often need to move its public folders to Office 365 Groups. Though public folders are quite an old component, Groups have been introduced recently. In this post, we will take you through the complete method of migrating Exchange Public Folders to Office 365 Groups. This is the native process offered by Microsoft through Mailbox Replication Service.

Migrating Public Folders to Office 365 with MRS

According to the current policy of public folder migration, Microsoft uses Mailbox Replication Service (MRS) and migration batches. MRS, that got introduced in 2010, allows asynchronous movement. It means that, while MRS is busy migrating the mailboxes users can continue with their tasks.

Here are the main features of MRS:

  • Export from Exchange old versions mailboxes.
  • Move mailboxes between different servers/ databases.
  • Transfer old public folders into new ones.
  • Migrate mailboxes and public folders of on-premises Exchange to Exchange Online.

This process supports source public folders that belong to on-premise Exchange Server versions 2016, 2013, 2010 or Exchange Online. For on-premises public folders, a functioning Exchange hybrid configuration should be available. Migration to Yammer groups is not possible.

Submit Migration Jobs to MRS

This method contains the similar steps of other migration batches. Create a CSV file containing public folders and their destination Groups in two columns to submit into MRS. Make sure to create the target Groups before the process begins.
Now, MRS will first connect to the public folder according to the full path you have provided (\Email\Archive for Exchange Discussions) and migrate its complete contents to the Office 365 Group using the primary SMTP address (
When done, submit the CSV file to MRS to consider it as the migration batch parameter using the New-MigrationBatch cmdlet.
It is not possible to join multiple public folder items and transfer them into a group at a time. For consolidation process, you need to perform multiple migration batches to the same Group.

Migrate Public Folder Contents

At this point, MRS will fetch the data from Source public folders and put those into the target groups. The progress can be checked using Get-MigrationBatch cmdlet or migration section of EAC. After it is completed, a complete migration report will be available for download from EAC. Here is the sample of the report.

Post-Migration Tasks

Even after the move is completed, the source public folders still exist and users have two more tasks to conduct.

a. Run “LockAndSavePublicFolderProperties.ps1 script” to lock the public folder. This will prohibit anyone from adding any data to those public folders. This script copies public folder SMTP address to the new group so that any email being sent to the public folder gets forwarded to the group.

Make sure to perform the complete migration procedure including properties switching when public folder is having low usage.

b. Another remaining task is to migrate the public folders permissions into group membership. Since office 365 Group has only two types of permissions (owner/member,) public folder owners, publishing editors, and publishing editors of public folder will become group owners. Everyone else will become the Group members.

The migration has been done completely now, so you can ask users to start using the new Group. The group contains all the old data and new emails will get delivered there too. Delete the public folder after some days when you become sure that there is no need to go back to old public folder.

Some Downsides of This Technique

The use of MRS for the purpose of public folder export is a reasonable decision since it is pointless to create another tool for this purpose only. However, here are some points that require a second thought.

1. This approach enables migration of public folders that contain email and calendar entries. Public folders with tasks and application are not suitable for this method.

2. This approach is not suitable for the migration of all public folders of Exchange server. Rather, it is most suitable for exporting selective public folders. In one sense this is good because most of the exchange public folders do not qualify to become Office 365 Group.

3. During public folder migration, MRS may encounter some bad items as some public folders contain very old data. In that case, the migration process gets halted because the migration batch must not contain any bad items. However, users can perform force migration by increasing the BadItemLimit parameter. Then there will be no option to see what is happening to those bad sectors. MRS does not offer any option to log what happens to these bad items, which is a drawback of this process.

4. After the migration is done, users need to use Outlook 2016 or Outlook Web App to access the Groups, as other older versions do not support Office 365 Group.

Manually Moving Public Folders to O365 Groups

  • The actual migration procedure will include these steps:
  • Locate the public folders you need to move.
  • Note down the identity and mailbox of public folders.
  • Make Office 365 groups as the destination of this transfer process.
  • Create a CSV file with the migration batches.
  • Add those batches to Mailbox Replication Service (MRS).
  • Conduct incremental synchronizations if needed.
  • Now, lock the old Exchange public folders and export their properties to the Groups of Office 365.
  • Finally, terminate the source public folders.

The steps discussed here are simple but can become the source of boredom if done repetitively.


Here, we have described the complete procedure to migrate Exchange public folders to Office 365 groups. Despite its limitations, this method is still considered as the most suitable one as it is the native solution provided by Microsoft.