Exchange must have auto-forwarding of email to remote domains disabled or restricted.

From Microsoft Exchange 2016 Edge Transport Server Security Technical Implementation Guide

Associated with: CCI-001368

SV-95201r1_rule Exchange must have auto-forwarding of email to remote domains disabled or restricted.

Vulnerability discussion

Attackers can use automated messages to determine whether a user account is active, in the office, traveling, and so on. An attacker might use this information to conduct future attacks. Ensure Automatic Forwards to remote domains are disabled, except for enterprise email that must be restricted to forward-only to .mil and .gov. domains.Before enabling this setting, first configure a remote domain.

Check content

Non-Enterprise Mail Check Content: Open the Exchange Management Shell and enter the following command: Get-RemoteDomain | Select Name, DomainName, Identity, AutoForwardEnabled If the value of "AutoForwardEnabled" is not set to "False", this is a finding. Enterprise Mail Check Content: Open the Exchange Management Shell and enter the following command: Get-RemoteDomain | Select Name, DomainName, Identity, AutoForwardEnabled If the value of "DomainName" is not set to a ".mil" and/or ".gov" domain(s) and the value of "AutoForwardEnabled" is not set to "True", this is a finding.

Fix text

For Non-Enterprise Mail Fix Text: Open the Exchange Management Shell and enter the following command: Set-RemoteDomain -Identity <'IdentityName'> -AutoForwardEnabled $false Note: The value must be in single quotes. For Enterprise Mail Fix Text, enter the following commands: New-RemoteDomain -Name -DomainName Note: NewDomainName must be either a ".mil" or ".gov" domain. Set-RemoteDomain -Identity <'IdentityName'> -AutoForwardEnabled $true

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