To enable distribution group support

1. Log on to a computer running the Office Communications Server administrative tools. To enable distribution group support you must be a member of both the Domain Administrators group and the RTCUniversalServerAdmins group.
   
   
2. Click Start, point to Administrative Tools, and then click Office Communications Server 2007 R2.
   
   
3. In the console tree, expand the forest node.
   
   
4. Expand Standard Edition Serversand right-click the name of the server on which Communicator Web Access is installed.
   
   
5. Click Propertiesand then click Web Component Properties.
   
   
6. In the Web Components Propertiesdialog box, on the Address Booktab, verify that Enable distribution groups expansionhas been selected, and that the desired value has been entered in the Maximum group sizebox.
   
   
7. Make any changes as needed, and then click OK.