Update 4/23/2018: Please see this post for the latest announcement on this subject.
Last September, we announced a beta program to validate onboarding of public folder data from Exchange 2010 on-premises to Exchange Online with large public folder hierarchies (100K – 250K public folders).
We are glad to announce that Exchange Online now officially supports public folder hierarchies of up to 250K public folders in the cloud – more than double the previously supported limit of 100K public folders!
In line with our efforts to help larger customers onboard to Exchange Online, we would like to additionally announce support for the migration of public folders from on-premises Exchange 2010 to Exchange Online, for customers with folder hierarchies up to 250K.
What does all this mean?
All existing customers using Exchange Online who would have been constrained by the limit of 100K public folders, can now expand their Exchange Online public folder hierarchy up to 250K folders.
Any on-premises customers running Exchange 2010 with up to 250K public folders, who would like to onboard to Exchange Online, can now do so.
Note: At this point in time, Exchange 2013/2016 customers with over 100K folders can still only migrate up to 100K public folders to Exchange Online. However, once they have migrated to Exchange Online, they can expand their hierarchy up to 250K public folders. We are working to resolve this limitation for our Exchange 2013/2016 customers in the future.
Keep checking this blog for further updates on the subject.
Public folder team