Last year's beta program, for customers looking to migrate very large Exchange 2010 on-prem Public Folder hierarchies to Exchange Online, has yielded an officially supported increase to 250,000 Public Folders on the ExO side. Prior, the limit for Exchange Online was 100,000 folders, and this was a migration blocker for many organizations.

Today's announcement is pertinent to customers with E2010 on-prem, and provides one more good reason to migrate PF content to the cloud and enjoy the benefits of Modern Public Folders. For those running newer Exchange on-prem versions, Microsoft notes that it is working to resolve this for E2013/E2016 organizations.