You need to control which accounts can send email messages to a distribution group.
Log on to any machine in your domain that has the Exchange management tools installed.
Open the ADUC snap-in (Users and Computers.msc).
Browse to the OU or domain where your groups are located.
Right-click the distribution group or mail-enabled security group, click Properties, and select the Exchange General tab.
By default, the group is set to allow mail From everyone. If you want to allow mail only from certain users, select Only from; if you want to exclude mail from certain users or groups, select From everyone except.
If you selected Only from or From everyone except, click Add, then select the desired user, group, and contact objects, and click OK to define which users are permitted or excluded.
For Exchange Server 2003 only, check the From authenticated users only checkbox if you want Exchange to ensure that a message has been submitted by an authenticated user. Click OK.
' This code displays the sender restrictions on a group object. ' ------ SCRIPT CONFIGURATION ------ const cdoexmAccept = 0 ' Included senders const cdoexmReject = 1 ' Excluded senders strGroupDN = "
<GroupParentDN>" ' e.g., cn=Staff,dc=3sharp,dc=com ' ------ END CONFIGURATION ------ ' Prepare the address list array Dim arrAddress() intSize = 0 ' Create the group object set objGroup = GetObject("LDAP://" & strGroupDN) ...