Exchange 2013 CU8 - Public Folders Limits - some limits updated for “modern” Public Folders in CU8


UPDATE 1 3/19/2015: The Exchange Product Team updated the Exchange 2013 CU8 announcement page with the new PF limits I’m also exposing below – see link and pasted update at the end of this post

UDATE 2 3/19/2015: The TechNet Public Folders Limit has been updated too with the new limits – checkout the link later on this post as well.  


Hi all,

Here are the new limits introduced by the Exchange 2013 Cumulative Update 8 (CU8) ( thanks very much to Brian Day – Senior Program Manager for confirming these with the PF team )


Public Folders - IconCU8 now supports the following for Public Folder scale:

· When migrating from legacy Exchange versions we support migrating up to 500,000 folders from 2007/2010 to 2013 CU8.

· Once using PFs on Exchange 2013 we support up to 1,000,000 folders in up to 100 Public Folder Mailboxes (this last one is the same as before) .

· We support up to 100,000 folders per Public Folder mailbox. This includes deleted PFs that have not yet aged out of the system.


  • Some more information in addition that remain true as well:

    . We should not be putting any PFs into the primary public folder mailbox.

    . We should not be allowing the primary public folder mailbox to serve hierarchy to clients (Set IsExcludedFromServingHierarchy to $True on primary PF mailbox).

    . Large organizations may also need PF mailboxes dedicated to serving hierarchy and other PF mailboxes dedicated to serving content.


  • More useful considerations for E2013 Public Folders (thanks again to Brian Day)
  1. Do not put content in the primary PF mailbox and exclude it from serving hierarchy.
  2. Create 1 PF mailbox for every concurrent 2,000 Outlook users for hierarchy purposes alone (note: while Exchange 2013 on premise supports twice more Public Folders mailboxes than Exchange Online in O365, Exchange 2013 on-premise public folder mailboxes cannot sustain 2000 concurrent connections). Do not put content in these PF mailboxes.
  3. Exclude all other PF mailboxes from serving hierarchy so only those created in step 2 are serving it
  4. And ideally you wouldn’t hold all PF mailboxes in same physical DB

Hierarchy replication would be slower and user experience may not be optimal if the above are not carefully considered.


In Exchange 2013 CU8 we are also delivering another milestone of public folder scalability improvements for our on-premises customers. When you are migrating from legacy versions of Exchange 2007/2010 to Exchange 2013 CU8 we now support migrating up to 500,000 public folders, a 200% increase from CU7. After your migration to Exchange 2013 CU8 has completed, or you are starting in a greenfield deployment of Exchange 2013 CU8, we now support up to 1,000,000 public folders, a 400% increase from CU7. The number of supported public folder mailboxes remains at 100 for the time being. In addition no single public folder mailbox in the organization may contain more than 100,000 public folders. The 100,000 value includes both active and deleted public folders stored within the public folder mailbox that have not yet aged out of the system due to your configured deleted public folder retention settings. Please remember that on-premises public folder scale limits are not the same as those used in Exchange Online. Exchange Online limits can be found at this article, and this documentation will be updated in the near future to reflect Exchange 2013 CU8 on-premises’ new limits.






The above article highlights some new improvements :

    • Calendar and Contact Modern Public Folders favorites added in Outlook are now accessible in OWA
    • Batch Migration of Public Folders to 2013 improves migration throughput and PF migration experience
    • Smoother migration for EAS clients to O365 with automatic profile redirect upon successful Hybrid migration to O365 (EAS client must support HTTP 451 redirect)


  • Other notes :

- Upgrading from Cumulative Update 7 to Cumulative Update 8 does not include Active Directory schema updates(see Exchange 2013 Active Directory schema changes and Prepare Active Directory and domains articles confirming this)

- Thanks to Hans Moser (Swiss MS PFE) for the below confirmation through testing as well:

The versions are still the same like in CU7, so there was no change.

  • And finally as a reminder:

- Exchange 2013 CUs are full bits of the Exchange product, so you can directly install Exchange from scratch (for new environments or new servers) using the above mentioned CU8 download, as well as apply the CU8 just like an “old school” service pack or patch, using your regular update procedures.