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

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-228356	SRG-APP-000038	EX16-MB-000030	SV-228356r879533_rule	2023-12-18	2

Description
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.

ℹ️ Check
Note: Requirement is not applicable on classified or completely closed networks. 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.

ℹ️ Check

Note: Requirement is not applicable on classified or completely closed networks. 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
Non-Enterprise Mail Fix Text: Open the Exchange Management Shell and enter the following command: Set-RemoteDomain -Identity <'IdentityName'> -AutoForwardEnabled $false Note: The <IdentityName> value must be in single quotes. Enterprise Mail Fix Text: New-RemoteDomain -Name <NewRemoteDomainName> -DomainName <SMTP Address> Note: <NewRemoteDomainName> must either be a .mil or .gov domain. Set-RemoteDomain -Identity <'RemoteDomainIdentity'> -AutoForwardEnabled $true Note: The <RemoteDomainIdentity> value must be in single quotes.

✔️ Fix

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