Hiding Distribution Group Membership – Exchange 2010 Thet method provided by Microsoft is to use Dynamic Distribution Groups which enumerate the group membership based on an LDAP query for a particular attribute being set on the user object, therefore membership is determined by the Hub Transport server at the point it is delivering the message. If you do not wish to convert to dynamic groups, there is an alternative method, whereby an attribute on the Distribution Group object, which is accessible via ADSIEdit, named ‘hideDLMembership’ can be set to true, which will prevent the expansion of groups in Outlook and OWA. Log In to the Exchange server Open Adsi edit connect to exchnage server browse to DL and do as directed below Attempting to expand the DL membership in Outlook will give the following error message: