In Office 365, a Public Folder mailbox has a size limit of 100GB.
For large Public Folder migrations exceeding 100GB, additional Public Folder mailboxes must be created to split the storage of this large amount of data. Therefore, we analyze the source environment, create multiple Public Folder mailboxes, and assign specific folders to these additional mailboxes. Microsoft recently changed a mechanism in O365, and therefore has impacted our typical functionality.
This approach is no longer functioning as expected. Currently, all the data, is ingested into the primary Hierarchy mailbox directly. When the synchronization reaches the 100 GB limitation, the migration will stop. Microsoft will now generate a single additional public folder mailbox and moves the content to it. This frees up storage of the Primary Hierarchy mailbox but this process takes up to 2 additional weeks and the synchronization cannot continue in the meantime. Once the move of the data from the primary hierarchy mailbox is complete, the synchronization can resume until again the 100GB limit is reached, and the same process will repeat.
We are working with Microsoft on a solution and hope to have one soon.
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