Dynamic Distribution Groups

Unlike a regular distribution group, a dynamic distribution group, as the name implies, is dynamic in nature. Whereas a regular distribution group is composed of a defined set of members, the membership list for a dynamic distribution group is calculated every time a message is sent to it. This is accomplished by utilizing a Lightweight Directory Access Protocol (LDAP) query that has been defined and assigned to the group. For example, you can build a dynamic distribution group that is intended to include all recipients in a particular state. Each time the list is accessed, the membership would be built based on information gathered from the AD.

Dynamic distribution groups require less maintenance than standard groups because the query is defined once, and the membership is built automatically every time the group is called. However, a performance cost is associated with their use, especially if the query produces a large number of results. Every time an email is sent to a query-based distribution group, server and domain resources are utilized to determine its membership.

Dynamic distribution groups are an extremely functional tool but should be used with discretion.

Creating Dynamic Distribution Groups in the EMC

To create a new dynamic distribution group in the Exchange Management Console, perform the following steps:

1. Start the Exchange Management Console.
2. In the Console Tree, navigate to the Recipient Configuration \ Distribution Group node.
3. In the action pane, click New Dynamic Distribution Group. The New Dynamic Distribution Group Wizard appears.
4. On the Introduction page, complete the following fields:
   • Organizational Unit-By default, the New Distribution Group will be created in the Users Organizational Unit (OU) in AD. To change the default OU, select the box labeled Specify the Organizational Unit Rather Than Using a Default One; then click Browse and select the desired OU.
   • Name-Enter the desired name for the group.
   • Alias-Enter the desired alias for the group. This is the name that will be used to generate the default email address for the distribution group, so it must only contain characters that can be used in a valid SMTP address. (For example, no spaces can be used.) If you select an invalid character, the wizard notifies you. Enter the desired alias.
5. Click Next.
6. On the Filter Settings page, complete the following fields:
   • Recipient container-By default, recipients from the entire organization are eligible as members of the distribution list. However, you can specify to include only members from a specific OU, if your OU structure matches the needs of the distribution list. For example, if you have an OU container for all employees in Europe, and you create a distribution group that contains only employees in Europe, specifying that OU prevents the list from searching the rest of AD every time a message is sent to the list. If you select an OU here, that OU and all OUs under it are included. To select an OU, click Browse and do so.
   • Include these recipient types-Either leave the default All Recipient Types, or, if desired, you can limit the group membership to one of the following categories:
     • Users with Exchange Mailboxes
     • Users with external email addresses
     • Resource mailboxes
     • Contacts with external email addresses
     • Mail-enabled groups
     • Or any combination of the above
7. When you are ready, click Next to continue.
8. On the Conditions page, you can select the conditions that will build the LDAP query that will identify the recipients to be included in the list. Select one or more conditions by placing a check in the associated box and then editing the conditions by selecting an underlying value. For example, if you were to select Recipients in a State or Province, you would then click the highlighted word and enter the value.
9. When you are ready, click the Preview button to test the query you created and ensure the membership of the list is populated as you expect. Click OK and, if all is as expected, click Next.
10. Review the configuration summary. If all is well, click New.
11. On the Completion page, the summary states whether the distribution group was successfully created and shows the Exchange Management Shell command that was used to create the distribution group. When ready, click Finish.

Creating Dynamic Distribution Groups in the EMS

To create a new distribution group in the Exchange Management Shell, a sample command is shown here: