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

From Microsoft Exchange 2016 Mailbox Server Security Technical Implementation Guide

Part of SRG-APP-000038

Associated with: CCI-001368

SV-95337r1_rule Exchange auto-forwarding email to remote domains must be 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. Verify Automatic Forwards to remote domains are disabled, except for enterprise mail that must be restricted to forward only to .mil and .gov. domains.Before enabling this setting, configure a remote domain.

Check content

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

Fix text

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. Enterprise Mail Fix Text: New-RemoteDomain -Name -DomainName Note: must either be a .mil or .gov domain. Set-RemoteDomain -Identity <'RemoteDomainIdentity'> -AutoForwardEnabled $true Note: The value must be in single quotes.

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