Exchange 2007 Distribution Groups

Before Microsoft Exchange Server became so closely connected to Active Directory (AD), administrators had to use static distribution lists to manually handle list memberships. Starting with Exchange Server 2000, AD was directly integrated into Exchange. Exchange Server 2003 saw the creation of distribution groups (and query-based distribution groups), which are populated by static memberships. Exchange Server 2007 introduced dynamic distribution groups, which are defined by filters and conditions each time a message is sent to the group. In this article I explain how to create traditional static distribution groups and Exchange 2007 dynamic distribution groups.

Types of Distribution Groups
Whether you create your own distribution groups, or they are pulled from a previous version of Exchange during a migration, four distinct types of distribution groups exist (beyond what you might think of as simply static versus dynamic groups). Exchange Management Console (EMC) displays these four types of distribution groups and represents each with a separate icon.

Creating a Traditional Distribution Group
To create a new distribution group, perform the following steps:

1.     Open EMC.

2.     From the navigation tree in the left-hand pane, select the Recipient Configuration container and click Distribution Group.

3.     In the Actions pane you’ll see two options for creating distribution groups: New Distribution Group and New Dynamic Distribution Group. Select New Distribution Group.

4.     The wizard’s Introduction dialog box gives you the option of creating a distribution group for a new or existing group. If you have an existing universal security group that isn’t mail-enabled, you can browse to the group and configure it as a Mail-Enabled Universal Security Group. You can also create a new distribution or security group. If you don’t have the administrative permissions to directly create a security group or handle its membership, you can work with your AD administrators to ensure that the group exists on the AD side, then use EMC to mail-enable the group on the Exchange side. In this case, select New Group.

5.     In the Group Information dialog box, which Figure 1 shows, enter the following information:

a.     Group type: Select Distribution

b.    Organizational unit: Browse to select a location

c.     Name: Enter the group name, which can’t exceed 64 characters

d.    Name (pre-Windows 2000): Because of legacy naming, this name is automatically populated by the Name field and should be correct.

e.     Alias: By default, the alias is the same as the distribution group’s name. You can change the alias, which you might do if you want to give the group an alternative name (e.g., if you want the alias to be unique compared with the AD-oriented security group). Like the name itself, the alias can’t exceed 64 characters. In addition, the alias must be unique within the forest.

f.     Click Next when you finish entering information in the Group Information dialog box.

6.     In the New Distribution Group dialog box that opens, review the configuration summary to confirm the information, then click New.

7.     Once the group is created, you’ll see a Completion screen with a green check mark that says Completed. Click Finish.

After you create a new distribution group, it will appear under your Recipient Configuration, Distribution Group node, as well as in the Microsoft Management Console (MMC) Active Directory Users and Computers snap-in. If you open the group from Active Directory Users and Computers, you can see that it’s a universal distribution group. If you select the Members or Member Of tabs (from Active Directory Users and Computers or from EMC), you’ll see that the tabs are empty because the group is brand new. You must to specify the membership.

Mail-Enabling a Distribution Group
To mail-enable a preexisting group, perform the following steps:

To add members to or remove members from a distribution group, open the group from the Recipient Configuration, Distribution Group node (or from Active Directory Users and Computers). Select the Members tab and click Add to add a member. To remove a member, select the user and click the X.

1.     Open EMC.

2.     From the navigation tree, select the Recipient Configuration container and click Distribution Group.

3.     In the Actions pane, select New Dynamic Distribution Group to begin the wizard.

4.     In the Introduction dialog box, you can select an organizational unit (OU) in which to place the group. The default OU is Users; click browse to select a different container. Provide a name and alias for the group, and click Next.

5.     In the Filter Settings dialog box, you must select the recipient container where you want to apply the filter. Again, the default is Users but you can click Browse to locate a different container and more narrowly define the group to an OU. Depending on your AD organizational structure, this setting can reduce the load on the Exchange server in determining how to apply precanned filters. You must also specify whether to include all recipient types or specific recipient types, such as the following:

a.     Users with Exchange mailboxes

b.    Users with external email addresses

c.     Resource mailboxes

d.    Contacts with external email addresses

e.     Mail-enabled groups

Click Next after making your selections.

6.     In the Conditions dialog box, which Figure 2 shows, the initial conditions (i.e., precanned filters) include Recipient is in a State or Province, Recipient is in a Department, and Recipient is in a Company. You can also establish values for various custom attributes. After you select a condition in Step 1, you edit or specify the condition in Step 2. For example, you might select the condition Recipient is in a Department, then specify the Marketing department. For more information about configuring custom attributes, see the sidebar “Custom Attributes in Exchange Server 2007 Dynamic Distribution Groups.”

7.     You can click the Preview button to see which users will be in the dynamic distribution group you created, based on filter settings and conditions. Click Next when you’re done configuring conditions.

8.     Review the configuration summary and click New.

9.     Once the group is created, you’ll see the green Completed check mark. Click Finish.

After you create a dynamic distribution group, you can change the group’s filter and condition settings in EMC. Although the group will also have an AD object, you won’t be able to configure its properties through Active Directory Users and Computers.

Because dynamic group membership is calculated every time a message is sent to the group, an individual might be part of a group one moment and not part of the group the next moment if the individual falls out of the group’s recipient scope. You should use dynamic groups sparingly because of the increased load placed on the server that is tasked with comparing your predefined criteria to the list of recipients.

Configuring Expansion Servers
Although distribution groups typically reduce administration costs and time, they also require more server resources in terms of CPU and RAM. The Hub Transport servers typically take the performance hit, because these servers are used in recipient resolution (i.e., the process by which recipients of a message are expanded and resolved). Messages are received in the Hub Transport server’s Submission queue and are then categorized by the categorizer or resolver before being placed in the Delivery queue. These transactions can occur hundreds or even thousands of times every day.

By default, distribution groups are expanded on any server in an organization. To prevent mail flow impediment, you might want to select a specific expansion server for very large distribution groups. To do so, perform the following steps:

If you select a specific server for your distribution group expansion, you might run into problems if the server is offline when a message is sent to that group. The message will sit in the queue and won’t be delivered. If you’re planning to perform server maintenance, be sure to change the expansion server for the groups that will be affected.

When you select an expansion server, you can also configure the following settings:

Distribution Direction
The benefit of Exchange 2007 distribution groups is that users can use one email address to reach multiple recipients. The caveat for administrators is that your servers can take a big performance hit when large groups are expanded out for recipient resolution. However, the positive aspects of Exchange 2007 distribution groups far outweigh the negative—so, go forth and distribute.