To Configure External Automatic Replies on individual users in Exchange Server 2010
By default, external automatic reply message is enabled in Exchange Server 2010, which allows all users to send external automatic messages. We can configure Exchange Server 2010 in such a way so that only selected users or groups can send external automatic messages.
Note: We cannot use Exchange Management Console to enable external automatic replies.
Below command will enable the external automatic reply message for Trenovision mailbox.
Set-Mailbox “Trenovision ” –ExternalOofOptions External
