This Knowledgebase article provides information about Public folder replication when deploying Neverfail for Exchange.
In all versions of Exchange, there exists the ability to replicate Public folders and their contents between Exchange servers in the enterprise.
There is a school of thought by some administrators that using Public folders as a shared filing system is better than network shares as it gives a single point of access to shared files and the files may be replicated around the Exchange servers.
Replication of Public folders is normally scheduled every 2 to 4 hours or possibly more frequent and as such if the Public folder hierarchy is being used as a file system, numerous changes may occur within these periods requiring a high volume of replication to be applied to the Public folders, which consequently needs replication to the Secondary server by Neverfail.
In addition, Exchange performs Public folder replication on an item level (i.e., at the message or document level) and does not support delta changes. Thus, if a change was made, such as one word in a large Microsoft PowerPoint presentation or Microsoft Word document held in a public folder, Exchange must replicate the complete item by bundling the entire file into discrete email messages, sending the email messages to the Public Folder Store that holds the replica, unbundling the messages, and applying the content to the Public Folder Store. This means that Neverfail in turn must replicate the entire item.
When installing Neverfail for Exchange, bear this in mind and check through the system attendant, which Public folders are being replicated and what they are being used for.