Learn more about creating public folder mailboxes in Exchange Online
Applies to: Exchange Online
If you don’t already have public folders in your Exchange Online organization, you can create the first public folder mailbox. The first public folder mailbox that you create is known as the primary public folder mailbox, and it contains the only writable copy of the public folder hierarchy. After the primary public folder mailbox is created, you can create public folders. As the content of the public folders increases beyond the capacity of the public folder mailbox quotas, Microsoft automatically creates new public folder mailboxes to accommodate the size of your public folders.
For more information about creating public folders in Exchange Online, see the following resources:
Public folders in Office 365 and Exchange Online
Create a public folder mailbox
If you plan to migrate your on-premises public folders to Exchange Online, you will use Windows PowerShell to create sufficient public folder mailboxes. The public folder mailboxes creation is based on the output from a PowerShell script that helps you migrate the public folders. For more information, see Public folders in Office 365 and Exchange Online.