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V-259706

CAT II (Medium)

Exchange must not send nondelivery reports to remote domains.

Rule ID

SV-259706r961620_rule

STIG

Microsoft Exchange 2019 Mailbox Server Security Technical Implementation Guide

Version

V2R3

CCIs

CCI-002385

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 that nondelivery reports to remote domains are disabled. Before enabling this setting, first configure a remote domain using the Exchange Management Console (EMC) or the New-RemoteDomain cmdlet.

Check Content

Note: For the purpose of this requirement, "remote" refers to those domains external to the DODIN, whether classified or unclassified. NDRs between DODIN networks is permitted.

Open the Exchange Management Shell and enter the following command:

Get-RemoteDomain | Select-Object -Property Name, Identity, NDREnabled

If the value of "NDREnabled" is not set to "False", this is a finding.

Fix Text

Open the Exchange Management Shell and enter the following command:

Set-RemoteDomain -Identity <'IdentityName'> -NDREnabled $false

Note: The <IdentityName> value must be in quotes.