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:
- Open EMC.
- From the navigation tree, select the Recipient Configuration container and click Distribution Group.
- Select the distribution group or dynamic distribution group from the Results pane.
- Select Properties in the Actions pane, and click the Advanced tab.
- As Figure 3 shows, the default Expansion server setting is Any server in the organization. You can use the dropdown list to select a particular Hub Transport server to handle the expansion list.
- Click OK to finish the process.
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:
- Hide group from Exchange address lists—Users can send email messages to a group through its email address directly, but the group won’t show in the address lists.
- Send out-of-office messages to originator—If you send an email message to a group and someone in the group has his or her out-of-office message enabled, you’ll receive an out-of-office reply. Leave this check box blank if you want to reduce the amount of unnecessary traffic on your server.
- Send delivery reports to group manager—Only the distribution group manager will receive the nondelivery report.
- Send delivery reports to message originator—This is the default setting.
- Do not send delivery reports—This option can minimize unnecessary traffic.
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.