EX16-MB-000300 - Exchange email-forwarding SMTP domains must be restricted.
Auto-forwarded email accounts do not meet the requirement for digital signature and encryption of Controlled Unclassified Information (CUI) and Personally Identifiable Information (PII) in accordance with DoDI 8520.2 (reference ee) and DoD Director for Administration and Management memorandum, 'Safeguarding Against and Responding to the Breach of Personally Identifiable Information'. Use of forwarding set by an administrator interferes with nonrepudiation requirements that each end user be responsible for creation and destination of email data.
Update the EDSP to specify any accounts that have been authorized to have email auto-forwarded or verify that this information is documented by the organization. Open the Exchange Management Shell and enter the following command: Set- RemoteDomain -Identity <RemoteDomainIdParameter>