Some things are just hard to understand. For example, why is anyone interested in Paris Hilton? Why doesn't the United States use the metric system? If a federal judge broke up AT&T 25 years ago, how come it's back together? Questions like these can provide endless puzzlement—and so can Microsoft's licensing scheme.

I want to preface the rest of this column with a confession: I'm not a Microsoft licensing expert. In fact, many people who work for Microsoft—and I'm talking about some very smart, talented people—don't understand its licensing policies and models. Out of sheer incompetence, I won't attempt to explain all the different types of licenses, contracts, agreements, and so forth. Instead, I'm sticking to an explanation of Exchange Server 2007 licensing, which has recently changed but is still a little confusing.

Start with the idea that each server running Exchange 2007 needs a server license. These come in two flavors: Standard Edition and Enterprise Edition. You can freely intermix the two within your organization. The primary difference is that the Enterprise Edition includes clustering and cluster continuous replication (CCR) support, as well as support for as many as 50 storage groups (SGs) and 50 databases. The Standard Edition lets you have as many as 5 SGs and 5 databases. In Exchange 2003, the Standard Edition server was limited to a 75GB database size; that limit disappears in the Exchange 2007 Standard license, which is a nice improvement. Typically you'd want the Enterprise Edition for Mailbox servers and Standard Edition licenses for all the other roles if they're on separate servers.

Exchange 2007 also requires one CAL per mailbox. The Standard CAL provides access to mailbox functionality (including mail, calendar, and contact functionality, OWA, and Exchange ActiveSync). The Enterprise CAL adds extra features:

  • unified messaging (UM)
  • the ability to journal messages for individual users or distribution lists (DLs)
  • the ability to define custom managed folders for message retention and archiving
  • permission to use Forefront Security for Exchange Server
  • access to the Exchange Hosted Filtering service for cleaning your inbound mail traffic of viruses, spam, and phishing attempts
  • premium antispam features for the Edge Trasport server role, including automatic antispam updates and the use of Microsoft's IP-based sender reputation service

The Enterprise CAL is an add-on to the standard CAL, not a standalone license. The tricky part comes in deciding how many Enterprise CALs you need. Here's the deal:

  • You need an Enterprise CAL for every mailbox on which you want to use UM, per-user or per-DL journaling, or managed custom folders.
  • If you want to use Forefront, Exchange Hosted Filtering, or premium antispam features, you need Enterprise CALs for all of your users.

These guidelines might seem a bit confusing, but after thinking about them for a while, I decided they make sense: It wouldn't be a good idea to enable the message hygiene features provided by Exchange Hosted Filtering, Forefront, and the Edge server for only a subset of your users; it does, however, make sense to provide UM, managed custom folders, and per-user journaling for only users who need them.

Microsoft recently made a change to the CAL structure, too. Managed default folders are now included in the standard CAL, so you can use the messaging records management toolset in Exchange 2007 against the Inbox, Calendar, Sent Items, and other default mailbox folders; you need the Enterprise CAL to define custom folders and put them under management.

There's still another Exchange 2007 licensing change that you need to be aware of: Exchange 2007 CALs don't include the right to use Microsoft Office Outlook. That's a topic for another day, but I'd love to hear your feedback on Exchange 2007 licensing and whether the revamped model is an impediment or an incentive for you to transition to the new version.