Public Folder Hierarchy Limits in Exchange Increased to 100,000

Microsoft announced this week that the public folder hierarchy limits of its Exchange Online service for Office 365 customers has increased.

The new public folder hierarchy limit is 100,000 folders, which is up from an earlier limit of 10,000 folders. This scaled-up capacity takes effect immediately for Office 365 customers, Microsoft indicated, in a Tuesday announcement.

Oddly, the public folder hierarchy expansion, which just refers to "the number of levels in the folder hierarchy of a mailbox," doesn't change Microsoft's quota on the number of public folder mailboxes that an organization can have. For Exchange Server 2013, the public folder mailbox quota is 100 public folder mailboxes, according to Footnote 9 in Microsoft's "Storage limits across Office 365 options" table, as found in this TechNet library article. For Office 365 plans, the quota limit is 50 public folder mailboxes.

Microsoft's folder limits descriptions for Exchange use specific terms that are bound to be confusing. Those terms can be found here.

Organizations using the premises-based Exchange Server 2013 product will get a public folders hierarchy boost, too, although they will have to wait until Microsoft releases Cumulative Update 6. Microsoft released CU5 in May and it tends to deliver its cumulative updates on a quarterly basis, so organizations could expect to see CU6 arriving maybe in August. Microsoft hasn't yet specified a release date yet for CU6, though.

Public folders let users share information. Users typically see a hierarchy of those folders within their Outlook e-mail clients. Those folders can be problematic for IT pros to track, particularly when they need to assess Exchange migrations. IT pros typically can't tell which folders are old and don't need to be moved. To count public folders in Exchange Online, Microsoft recommends using two PowerShell commands: Get-Public Folder and Measure-Object.

The earlier public folder hierarchy limit wasn't well known. Exchange users successfully petitioned Microsoft to increase the limit at the Microsoft Exchange Conference back in March.

Microsoft had indicated last month that it would increase the Office 365 public folder hierarchy limits. However, it's not altogether clear if the Exchange Server 2013 public folder hierarchy limit also will increase to 100,000 folders. Microsoft is still assessing the new limits possible for its premises-based server product.

Public folder hierarchy limits will continue to expand. Exchange Online could eventually support a million folders over time, Microsoft has claimed.

About the Author

Kurt Mackie is senior news producer for 1105 Media's Converge360 group.

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