But with public folder mailboxes, Microsoft is recreating the image of public folders.
It appears that this is a new beginning for public folders through a more reliable and supportable design.
https://technet.microsoft.com/en-us/library/Now Let’s Get Into the Real Details Regardless of whether your organization will migrate its public folders to Exchange Online a primary public folder mailbox will be required to get started.
Also be aware that if the data in your public folders increases above the capacity allowed within public folder mailbox quotas, Microsoft automatically creates new public folder mailboxes. Public Folder Mailbox Tab Learn More(EXCHG.150).aspx? v=22.214.171.124&l=1&s=BPOS_S_E15_0_Slim Additionally, in order to do public folder work within Exchange Online your administrator may need to verify that you have the appropriate permissions.
Honestly, 2.5 TB of public folder data is quite significant and in most cases it is difficult to consider this a limitation, but I am sure there is an organization somewhere that will not be able to move to cloud-based public folders even with this amount of capacity.