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With the release of Cumulative Update 1 for Exchange Server 2013, it became possible for 2013 to coexist with previous versions of Exchange. However, even with the first cumulative update release for Exchange 2013, you had two choices for your 20,000 public Folders. You could indefinitely keep the public folders on Exchange 2010, or reduce the number of folders to no more than 10,000 prior to migrating. That was the maximum number of public folders supported in the early versions of Exchange 2013.
The good news is that CU6, CU7 and now CU8 for Exchange 2013 have exponentially extended the support for when an organization decides to migrate public folders. CU8 now supports up to 500,000 public folders during a migration. Once the migration is complete, this number can increase to 1 million public folders in a pure Exchange 2013 organization. For organizations planning to migrate public folder data to Exchange Online (Office 365), the current limit is 100,000 public folders per tenant.
So what's the best way to migrate these larger counts of public folders? First, understand the support boundaries. Mailboxes homed on Exchange 2007 or Exchange 2010 servers cannot access public folders on an Exchange 2013 server. Clients can access public folders on Exchange 2013 only if their mailbox has moved to Exchange 2013 servers. All clients in any coexistence scenario can still access legacy public folders in Exchange 2007 or Exchange 2010 servers. It makes sense that public folders should be the last thing that you migrate if you want to maximize your end users' ability to access them.
Unfortunately, legacy public folders and Exchange 2013 public folders can't coexist in the same organization. When the time is right to migrate public folders, there will be a one-time cutover with some downtime during the final steps of the migration. I won't go into all the details of the migration, but I can outline a high-level process. To minimize the impact on end users, do as much as possible during off hours.
- Download migration scripts.
- Prepare for migration.
- Generate CSV files.
- Create public folder mailboxes.
- Start migration request.
- Lock down legacy public folders.
- Validate and unlock folders.
For more details on how to complete this, see the TechNet article on how to use serial migration to migrate public folders to Exchange 2013.
About the author:
Richard Luckett is a consultant and instructor specializing in messaging and unified communications. He's been a certified professional with Microsoft since 1996 and has 20 years of experience in the public and private sectors. He's a Microsoft Certified Trainer with more than 15 years of training experience with the Microsoft product line and received the Exchange MVP award in 2006, 2007 and 2008. He's also an expert in deploying and integrating Exchange Server and Lync Server. He leads the Microsoft training and consulting practice at LITSG.
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