Appendix B. Migrating Large Public Folders to Exchange 2013 (or Higher) and Office 365
Unlike Exchange versions 2010 and earlier, in Exchange 2013 or higher and Office 365 public folders are stored in public folder mailboxes, and size limit for such mailboxes is 100GB for Exchange organization and 50GB for Microsoft Office 365. Therefore, if public folder content in source organization is larger than the limit on the target, then to migrate it you will need to perform specific steps described in this section.
Important: Currently, Migration Manager for Exchange processes public folders of source Exchange 2013 or higher organizations as a single list of public folders ignoring their actual division by public folder mailboxes. Therefore, you need to plan public folder migration from an Exchange 2013 or higher organization according to information in this section in the same way as for Exchange 2010 and earlier organization.
Determining Public Folders Size
As a first step, you need to analyze the overall size of public folders that are planned to be migrated to Exchange organization. This can be done by reviewing information in Exchange System Manager (applicable to Exchange 2003) or by invoking theGet-PublicFolderStatistics cmdlet (applicable for Exchange 2007 or 2010).
- If the size is less than the size limit, you don’t need to follow the below procedures. Instead you can simply migrate all public folders to a single public folder mailbox using Migration Manager for Exchange. For more information, see Public Folder Synchronization.
- If the size is almost equal to or more than the size limit, you will need to split public folders into branches where each branch is less than the size limit and then migrate branches of public folders to separate Exchange public folder mailbox, as described in subsequent topics.
Planning Public Folder Migration
IMPORTANT: This section is applicable for migration scenarios supported by legacy Exchange Agents only. For migration scenarios supported by MAgE refer to the Public Folder Synchronization (MAgE) document.
This document contains information on two-way public folder synchronization using legacy agents in migration scenarios from Microsoft Exchange 2010/2013/2016 to Exchange 2016/2019 or to Microsoft Office 365. We do recommend the alternative method of two-way public folders synchronization by enhanced Migration Agent for Exchange (MAgE) combined with extended MMEx PowerShell module. Refer to Public Folder Synchronization (MAgE) document for details.
Prior to actual public folder migration, you need to plan how public folders should be migrated:
- Estimate how many Exchange public folder mailboxes you will need to keep your existing public folder content. Take into account that each public folder mailbox can contain up to 100GB of content for Exchange organization and 50GB for Microsoft Office 365, but some space is recommended to be left free. For example, if your source public folders size is 240GB, you need to have at least 3 public folder mailboxes in target Exchange organization or 5 public folder mailboxes in Microsoft Office 365.
- Analyze how to split public folders into branches where content of each branches is less maximum size limit and plan mapping those branches to target public folder mailboxes.
NOTE: If you migrate form Exchange 2007 or 2010, you can use the Export-PublicFolderStatistics.ps1 script to identify public folder sizes. That script creates file with public folders names and their sizes. For more information, see this TechNet article.
Migrating Public Folders
Now you can actually migrate public folders according to your migration plan by taking the following steps:
- According to your public folder migration plan, create public folder mailboxes in the target Exchange organization and in each of them create a root public folder where the corresponding branch of source public folders will be migrated. For that, use the following cmdlets:
New-Mailbox -PublicFolder -Name <mailbox_name>
New-PublicFolder -Name <public_folder_name> –Path <path_to_public_folder> -Mailbox <mailbox_name>
NOTE: Prior to creating public folders mailboxes for migration, ensure that your Exchange 2013 organization already has at least one public folder mailbox, or create it otherwise. That mailbox will be the primary hierarchy public folder mailbox.
- Configure a public folder synchronization job in Migration Manager for Exchange. For more information, see Public Folder Synchronization Process
- Add public folders collections with pairs of source public folder branches and corresponding root public folders according to your migration plan.
- Start public folders synchronization.
For more information, review information in the Sample Migration Scenario section that describes a real-world example of migrating large public folders to Exchange 2013.