Cannot send email to Groups in Exchange using contact created by the directory connector.
User receives a NDR stating 550 5.7.1 RESOLVER.RST.AuthRequired; authenticaion required
This is caused by a configuration on the receive connector.
Please verify that the receive connector has the following settings selected:
Externally Secured (for example, with IPsec) on the Authentication tab
Anonymous users and Exchange servers on the Permission Groups tab.