Limits for public folders

 

Applies to: Exchange Server 2016

Topic Last Modified: 2016-08-12

Summary: The supported limits for public folders in Exchange 2016.

In Exchange Server 2016, we public folders are based on a mailbox architecture, which allows public folders to benefit from things such as the resiliency of a Database Availability Group (DAG) and other mailbox enhancements. However, there are limits and performance considerations that should be taken into account.

The following table lists the limits for public folders in on-premises Exchange Server 2016. Unless the limits are specifically stated as recommended, the values listed in this table are the supported limits for public folders.

importantImportant:
Looking for Exchange Online limits for Office 365? See Exchange Online Limits.

 

Item Limits Notes

Total number of public folder mailboxes

1,000

1,000 is the limit for Exchange Server 2016 CU2 or later. Although you can create more than 1,000 public folder mailboxes, it isn’t supported. Create a public folder mailbox

Total public folders in hierarchy

1,000,000

Although you can create more than 1,000,000 public folders, it isn’t supported. For any deployment of 100,000 or more public folders, we recommend reading Considerations when deploying public folders.

Sub-folders under the parent folder

10,000

While you can create more than 1,000 sub-folders under a parent folder, we don't recommend that you do so.

FolderHierarchyChildrenCountReceiveQuota parameter on the Set-Mailbox cmdlet.

Folder depth

300

The folder depth is the number levels of nested folders that can exist in one branch of a public folder tree. FolderHierarchyDepthRecieveQuota parameter on the Set-Mailbox cmdlet.

Maximum messages per public folder

1 million

MailboxMessagesPerFolderCountRecieveQuota parameter on the Set-Mailbox cmdlet.

Maximum individual public folder size

10 GB

This limit doesn’t include subfolders beneath a single folder.

Configure storage quotas for a mailbox

Public folder mailbox size

100 GB

Configure storage quotas for a mailbox

Number of user logons per public folder mailbox

2,000 concurrent user logons

We recommend that you configure your hierarchy so that you have no more than 2,000 users per public folder mailbox. For example, if you have 20,000 users, you should have 10 public folder mailboxes.

Moved item retention

14 days recommended

Use the DefaultPublicFolderMovedItemRetention parameter on the Set-OrganizationConfig cmdlet.

Age limit

We recommend that you set this as the same default that you use for regular mailboxes.

These settings can be set at the following levels:

  • Organizational level: DefaultPublicFolderAgeLimit parameter on the Set-OrganizationConfig cmdlet.

  • Mailbox level: AgeLimit parameter on the Set-Mailbox cmdlet.

  • Folder level: AgeLimit parameter on the Set-PublicFolder cmdlet.

Deleted item retention

We recommend that you set this as the same default that you use for regular mailboxes.

These settings can be set at the following levels:

  • Organizational level: DefaultPublicFolderMovedItemRetention parameter on the Set-OrganizationConfig cmdlet.

  • Mailbox level: RetainDeletedItemsFor on the Set-Mailbox cmdlet.

  • Folder level: RetainDeleteItemsFor parameter on the Set-PublicFolder cmdlet.

Maximum number of public folders that can be migrated to Exchange 2016

500,000

This is the maximum number of public folders you can move to Exchange 2016 from a legacy version of Exchange in a single migration. For details on migrating public folders, see Use batch migration to migrate public folders to Exchange 2016 from previous versions.

 
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