Public folder contacts not updating
All other public folder mailboxes contain a not-writeable or secondary copy of the hierarchy that are updated by an Exchange mailbox assistant every 24 hours at a minimum, or every 15 minutes if clients are connected to a public folder mailbox that contains a secondary copy of the hierarchy.
Synchronization ensures that all of the public folder mailboxes present the same hierarchy to clients.
And of course, if you use public folders with Office 365, you won’t see any trace of these cmdlets because Microsoft takes care to maintain public folders in good health for its cloud tenants.
Update: If you’re interested in upgrading to Exchange 2013 and need to migrate some public folders to the modern format (or indeed, to migrate some public folders to Exchange Online in Office 365), then you might like to read my thoughts on the migration process. They continue to persist despite seemingly being on the edge of extinction several times.
By contrast, Exchange 2013 synchronizes public folder mailboxes by connecting to the mailbox that contains the primary hierarchy and adjusting a secondary copy based on the primary.
Synchronization is obviously tremendously important. Normally everything happens automatically and you should never have to interfere.
By reference to the writeable copy, public folder mailboxes that hold secondary copies learn about additions and removals of public folders and the mailboxes that hold public folder content.
The older form of public folders also synchronize information between databases but use replication messages for this purpose.Some companies have hundreds of thousands of folders in their public folder hierarchy, even if they don’t quite know what all the folders are used for, whether they still hold useful information, who created the folders in the first place, and what to do with them in the future.