You can replicate public folders to different servers in the same site or to servers in other sites. Replicating public folders to other servers is an effective way to balance the load of users viewing a particular public folder at a given time. For example, if you have 100 users and 3 public folder servers in a site and all 100 users are using one specific folder many times a day, this can create an excessive amount of traffic on that server. However, if you create a public folder replica on a second server, the information stores on both servers can balance the load of users.
The information store supports a multimaster replication model for public folders ¾ that is, you can make changes directly to any replica of a public folder or to messages within the folder, and these changes are then reflected in all other replicas. For example, when you modify a message or an attachment in a message in a public folder, the message and its attachments are replicated to all the other public folder instances. Changes are replicated at the document level, which means that if a single document is changed in a folder with hundreds of documents, only the document that is changed is replicated.
Public folder replication is e-mail based. This allows replicated instances of public folders to reside on information stores located on different physical local area networks (LANs) that are connected only by e-mail. The store-and-forward nature of message routing allows for replication message fan-out, that is, this minimizes network overhead when the number of replicas is high because of delayed splitting of recipient messages.