Update on Exchange Public Folders: What They Are

This is the first of a short series of bulletins on Exchange public folders. We discuss:

  • What they are and how they're used (this bulletin)
  • The problems of public folders (next bulletin)
  • The migration options and the main issues to consider when migrating (third bulletin)

What Public Folders Are
Public folders have been available since Exchange 4.0, which shipped in 1996. They represent an early attempt by Microsoft to provide a common space that users can work in. So they can be thought of as a precursor to SharePoint. In particular, public folders provide places where users can share email, files, calendars, and address book information.

Public folders are implemented as a MAPI folder hierarchy, potentially many folders deep. Most folders contain email messages, but in fact public folders can contain any Outlook/Exchange data type and conventional files.

As their name indicates, public folders are shared among users. Access controls can be defined on any part of the hierarchy, including the ability to delegate permission-setting to other users. Public folders reside on Exchange servers. To provide for ease of access for many users, they are typically replicated between different departmental servers.

To get a better feel for how they look from the user standpoint, see this 10-minute video.

How Public Folders Are Used
In a large organization, the top levels of the hierarchy typically represent a natural nesting of divisions, regions, departments, and so on, down to clusters of closely related users. The leaf folders contain actual information.

Common uses of leaf folders are:

  • Archives of email-based discussions on a topic.
  • Setting up meetings, through a shared calendar.
  • Sharing address book information.
  • Archiving emails with large attachments. Public folders aren't usually purged, so dragging an email over to a public folder is a way of keeping a copy. This frees up space in the user's main message store.
  • Storing of application-generated alerts.
  • Receiving email from outside. Public folders can be mail-enabled. So, for example, outsiders can send emails to sales-inquiries@megacorp.com, where staff can then respond.

In-house-developed public folder applications are also common, such as a help desk system, where forms are used to manage trouble tickets. The tickets are accessed via forms, and the information is stored in a public folder and its appropriate subfolder (e.g., "New Ticket," "Being Worked On," and "Resolved").

Finally, a variety of third-party applications are available that use public folders. An example is Pertrac's contact management applications, which are used by investment banking traders to share information about customers.

Access Controls
Two key roles must be defined:

  • Default. This is for most internal users, and defines what they can do. The default settings are normally set to give a lot of power to users, to create and manage public folders, and delegate permissions to others.
  • Anonymous. This is intended for external users, not identified in Active Directory. It lets them contribute items to a mail-enabled folder, but they cannot see it or modify the contents.

A wide variety of privileges can be assigned; administrator-only privileges include the definition of replication and limits settings. Access controls are inherited from higher folders, although they can be overridden.

... David Ferris and Rita Gurevich

Rita is founder of SPHERE Technology Solutions, a professional services organization that focuses on data management and clean-up initiatives in the Microsoft infrastructure.

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