You want to create a mail-enabled distribution group that automatically updates its membership based on rules you specify.
Log on to any machine in your domain that has the Exchange management tools installed.
Open the ADUC snap-in (Users and Computers.msc).
Navigate to the domain and container (or OU) that you want to host the new group.
Right-click the target container and choose the New→ Query-based Distribution Group command.
You can only create and use query-based distribution groups when your Exchange organization is in native mode and has Exchange 2000 SP3 or later on all servers. Your global catalog servers can be running Windows 2000 (with the DynamicDLPageSize key set; see MS KB 822897) or Windows Server 2003. If you try to perform step 4 while your organization is in mixed mode, you'll get a polite error dialog explaining that you must go native before creating any QDGs; if you don't adjust DynamicDLPageSize, you may find that QDGs aren't reliably expanded.
When the New Object - Query-based Distribution Group dialog appears, enter a name for the QDG; optionally, you can enter a separate alias (but if you don't, the name will be used as the alias). Click Next.
The filter specification dialog (see Figure 5-5) will appear:
Use the Change button to select the container scope that the QDG is restricted to; by default, the QDG will be restricted to the Users container in the domain ...