Do not process incoming mailslot messages used for domain controller location based on NetBIOS domain names
Verified with Windows 11 25H2 — updated on July 30, 2026
Supported on: At least Windows Vista
Path in the GPO console
Computer Configuration\Administrative Templates\System\Net Logon\DC Locator DNS Records Description
This policy setting allows you to control the processing of incoming mailslot messages by a local domain controller (DC). Note: To locate a remote DC based on its NetBIOS (single-label) domain name, DC Locator first gets the list of DCs from a WINS server that is configured in its local client settings. DC Locator then sends a mailslot message to each remote DC to get more information. DC location succeeds only if a remote DC responds to the mailslot message. This policy setting is recommended to reduce the attack surface on a DC, and can be used in an environment without WINS, in an IPv6-only environment, and whenever DC location based on a NetBIOS domain name is not required. This policy setting does not affect DC location based on DNS names. If you enable this policy setting, this DC does not process incoming mailslot messages that are used for NetBIOS domain name based DC location. If you disable or do not configure this policy setting, this DC processes incoming mailslot messages. This is the default behavior of DC Locator.
Registry
Software\Policies\Microsoft\Netlogon\Parameters Value name: IgnoreIncomingMailslotMessages
Enabled: IgnoreIncomingMailslotMessages = 1
Disabled: IgnoreIncomingMailslotMessages = 0
MDM / Intune (CSP)
./Device/Vendor/MSFT/Policy/Config/ADMX_Netlogon/Netlogon_IgnoreIncomingMailslotMessages Microsoft Learn documentation Mapping data: Microsoft Learn (CC BY 4.0)
Export Builder
BETAConfigure the state, scope and options, then generate .reg, PowerShell, Intune and SCCM outputs — or add the setting to a multi-setting collection.
These exports write the registry — this is not a managed GPO. ⓘ
.reg file
Windows Registry Editor Version 5.00
; Exported from gporais.com
; Policy: Do not process incoming mailslot messages used for domain controller location based on NetBIOS domain names
; State: Enabled
; Supported on: At least Windows Vista
[HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Netlogon\Parameters]
"IgnoreIncomingMailslotMessages"=dword:00000001More formats (PowerShell, Intune, SCCM)
PowerShell
# Exported from gporais.com
# Policy: Do not process incoming mailslot messages used for domain controller location based on NetBIOS domain names
# State: Enabled
# Supported on: At least Windows Vista
$path = 'HKLM:\Software\Policies\Microsoft\Netlogon\Parameters'
New-Item -Path $path -Force | Out-Null
Set-ItemProperty -Path $path -Name 'IgnoreIncomingMailslotMessages' -Value 1 -Type DWordIntune XML
OMA-URI: ./Device/Vendor/MSFT/Policy/Config/ADMX_Netlogon/Netlogon_IgnoreIncomingMailslotMessages
Data type: String
Value:
<enabled/>Intune Remediation
# === Detection script ===
# Exported from gporais.com
# Policy: Do not process incoming mailslot messages used for domain controller location based on NetBIOS domain names
# State: Enabled
# Supported on: At least Windows Vista
function Test-RegistryValue {
param(
[Parameter(Mandatory = $true)][string]$Path,
[Parameter(Mandatory = $true)][string]$Name,
[object]$Expected,
[ValidateSet('String', 'DWord', 'MultiString')][string]$Kind = 'String',
[switch]$Absent
)
try {
$item = Get-ItemProperty -LiteralPath $Path -Name $Name -ErrorAction Stop
} catch {
return $Absent.IsPresent
}
if ($Absent.IsPresent) { return $false }
$actual = $item.$Name
if ($Kind -eq 'DWord') { return ([int64]$actual) -eq ([int64]$Expected) }
if ($Kind -eq 'MultiString') {
$actualValues = @($actual)
$expectedValues = @($Expected)
if ($actualValues.Count -ne $expectedValues.Count) { return $false }
for ($i = 0; $i -lt $expectedValues.Count; $i++) {
if ([string]$actualValues[$i] -ne [string]$expectedValues[$i]) { return $false }
}
return $true
}
return [string]$actual -eq [string]$Expected
}
$checks = @(
(Test-RegistryValue -Path 'HKLM:\Software\Policies\Microsoft\Netlogon\Parameters' -Name 'IgnoreIncomingMailslotMessages' -Expected 1 -Kind DWord)
)
if ($checks -notcontains $false) {
Write-Output 'Compliant'
exit 0
}
Write-Output 'Non-compliant'
exit 1
# === Remediation script ===
# Exported from gporais.com
# Policy: Do not process incoming mailslot messages used for domain controller location based on NetBIOS domain names
# State: Enabled
# Supported on: At least Windows Vista
$path = 'HKLM:\Software\Policies\Microsoft\Netlogon\Parameters'
New-Item -Path $path -Force | Out-Null
Set-ItemProperty -Path $path -Name 'IgnoreIncomingMailslotMessages' -Value 1 -Type DWordSCCM scripts
# Exported from gporais.com
# Policy: Do not process incoming mailslot messages used for domain controller location based on NetBIOS domain names
# State: Enabled
# Supported on: At least Windows Vista
# SCCM Configuration Item guidance:
# Create a Configuration Item of type "Setting: Script".
# Discovery script: use the Detection script below.
# Remediation script: use the Remediation script below.
# Compliance rule: the Discovery script output equals 'Compliant'.
# === Detection script ===
# Exported from gporais.com
# Policy: Do not process incoming mailslot messages used for domain controller location based on NetBIOS domain names
# State: Enabled
# Supported on: At least Windows Vista
function Test-RegistryValue {
param(
[Parameter(Mandatory = $true)][string]$Path,
[Parameter(Mandatory = $true)][string]$Name,
[object]$Expected,
[ValidateSet('String', 'DWord', 'MultiString')][string]$Kind = 'String',
[switch]$Absent
)
try {
$item = Get-ItemProperty -LiteralPath $Path -Name $Name -ErrorAction Stop
} catch {
return $Absent.IsPresent
}
if ($Absent.IsPresent) { return $false }
$actual = $item.$Name
if ($Kind -eq 'DWord') { return ([int64]$actual) -eq ([int64]$Expected) }
if ($Kind -eq 'MultiString') {
$actualValues = @($actual)
$expectedValues = @($Expected)
if ($actualValues.Count -ne $expectedValues.Count) { return $false }
for ($i = 0; $i -lt $expectedValues.Count; $i++) {
if ([string]$actualValues[$i] -ne [string]$expectedValues[$i]) { return $false }
}
return $true
}
return [string]$actual -eq [string]$Expected
}
$checks = @(
(Test-RegistryValue -Path 'HKLM:\Software\Policies\Microsoft\Netlogon\Parameters' -Name 'IgnoreIncomingMailslotMessages' -Expected 1 -Kind DWord)
)
if ($checks -notcontains $false) {
Write-Output 'Compliant'
exit 0
}
Write-Output 'Non-compliant'
exit 1
# === Remediation script ===
# Exported from gporais.com
# Policy: Do not process incoming mailslot messages used for domain controller location based on NetBIOS domain names
# State: Enabled
# Supported on: At least Windows Vista
$path = 'HKLM:\Software\Policies\Microsoft\Netlogon\Parameters'
New-Item -Path $path -Force | Out-Null
Set-ItemProperty -Path $path -Name 'IgnoreIncomingMailslotMessages' -Value 1 -Type DWordBuilding a multi-setting collection? Add this setting and generate combined .reg / PowerShell / GPO scripts.