Enable remote mailslots

ComputerNative Intune settingPol_EnableMailslots

Supported on At least Windows Server 2025, Windows 11

25H2 · 1.0

What it does

This policy controls whether the SMB server will enable or disable remote mailslots over the computer browser service. If you disable this policy setting, the computer browser service will no longer run as expected. If you do not configure this policy setting, the computer browser may still be working with remote mailslots enabled. Note: This policy requires a Windows reboot to take effect.

What it writes

Hive: HKEY_LOCAL_MACHINE
Registry key: Software\Policies\Microsoft\Windows\Bowser
Value name: EnableMailslots
When enabled: DWORD 1
When disabled: DWORD 0

In Intune

Native Intune setting: Yes — Policy CSP

./Device/Vendor/MSFT/Policy/Config/LanmanServer/EnableMailslotsLanmanServer on Microsoft LearnNot yet in a released Windows build when Microsoft published these DDF files; Learn shows the release it shipped in.

From Microsoft's Policy CSP DDF files (DDF v2 Files, February 2026), read 18 Oct 2026.

Security baselines

Microsoft's Windows 11 v26H2 Security Baseline v2 sets this to Disabled, in its GPO “MSFT Windows 11 26H2 - Computer”.

Policy value EnableMailslots: Sets EnableMailslots to 0 (REG_DWORD).

Read from the registry.pol files in the baselines' GPO backups, downloaded from Microsoft's Security Compliance Toolkit. All baselines

Configure and deploy

Choose a state; the output below is generated from the template for exactly that.

Enabled · Computer · template defaults

Registry file (.reg)

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows\Bowser]
"EnableMailslots"=dword:00000001

PowerShell

$ErrorActionPreference = 'Stop'

function Set-RegistryValue {
    param(
        [Parameter(Mandatory = $true)][string] $Path,
        [Parameter(Mandatory = $true)][string] $Name,
        [Parameter(Mandatory = $true)][string] $PropertyType,
        [Parameter(Mandatory = $true)][object] $Value
    )

    if (-not (Test-Path -LiteralPath $Path)) {
        New-Item -Path $Path -Force | Out-Null
    }

    New-ItemProperty -LiteralPath $Path -Name $Name -PropertyType $PropertyType -Value $Value -Force | Out-Null
}

function Remove-RegistryValue {
    param(
        [Parameter(Mandatory = $true)][string] $Path,
        [Parameter(Mandatory = $true)][string] $Name
    )

    if (Test-Path -LiteralPath $Path) {
        Remove-ItemProperty -LiteralPath $Path -Name $Name -Force -ErrorAction SilentlyContinue
    }
}

function Clear-RegistryKeyValues {
    param(
        [Parameter(Mandatory = $true)][string] $Path
    )

    if (-not (Test-Path -LiteralPath $Path)) {
        return
    }

    foreach ($propertyName in (Get-Item -LiteralPath $Path).Property) {
        Remove-ItemProperty -LiteralPath $Path -Name $propertyName -Force -ErrorAction SilentlyContinue
    }
}

# Policy: Enable remote mailslots
# Name: Pol_EnableMailslots
# Scope: Machine
# State: Enabled
# Source: LanmanServer.admx

Set-RegistryValue -Path 'Registry::HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows\Bowser' -Name 'EnableMailslots' -PropertyType 'DWord' -Value 1

These deployment candidates come from the ADMX template; they are separate from the native CSP mapping above.

The OMA-URI is an inferred ADMX-backed Policy CSP candidate derived from the source ADMX file name and policy name.
Some Microsoft policies use built-in Policy CSP pages whose area names don't match the ADMX file name, so verify the candidate against Microsoft Learn before deployment.

ADMX profile candidate (OMA-URI)

./Device/Vendor/MSFT/Policy/Config/ADMX_LanmanServer/Pol_EnableMailslots

ADMX SyncML candidate

<SyncML xmlns="SYNCML:SYNCML1.2">
  <SyncBody>
    <Replace>
      <CmdID>1</CmdID>
      <Item>
        <Meta>
          <Format>chr</Format>
          <Type>text/plain</Type>
        </Meta>
        <Target>
          <LocURI>./Device/Vendor/MSFT/Policy/Config/ADMX_LanmanServer/Pol_EnableMailslots</LocURI>
        </Target>
        <Data>&lt;enabled/&gt;</Data>
      </Item>
    </Replace>
    <Final/>
  </SyncBody>
</SyncML>

Intune remediation scripts

Detection

$ErrorActionPreference = 'Stop'
$reasons = [System.Collections.Generic.List[string]]::new()

function Test-RegistryValueExists {
    param(
        [Parameter(Mandatory = $true)][string] $Path,
        [Parameter(Mandatory = $true)][string] $Name
    )

    if (-not (Test-Path -LiteralPath $Path)) {
        return $false
    }

    return $null -ne (Get-ItemProperty -LiteralPath $Path -Name $Name -ErrorAction SilentlyContinue)
}

function Test-RegistryValueEquals {
    param(
        [Parameter(Mandatory = $true)][string] $Path,
        [Parameter(Mandatory = $true)][string] $Name,
        [Parameter(Mandatory = $true)][string] $Kind,
        [Parameter(Mandatory = $true)][object] $Expected
    )

    if (-not (Test-Path -LiteralPath $Path)) {
        return $false
    }

    $valueObject = Get-ItemProperty -LiteralPath $Path -Name $Name -ErrorAction SilentlyContinue
    if ($null -eq $valueObject) {
        return $false
    }

    $actual = $valueObject.$Name
    switch ($Kind) {
        'String' { return [string]$actual -ceq [string]$Expected }
        'ExpandString' { return [string]$actual -ceq [string]$Expected }
        'DWord' { return [uint32]$actual -eq [uint32]$Expected }
        'QWord' { return [uint64]$actual -eq [uint64]$Expected }
        'MultiString' {
            $actualArray = @($actual)
            $expectedArray = @($Expected)
            if ($actualArray.Count -ne $expectedArray.Count) { return $false }
            for ($index = 0; $index -lt $actualArray.Count; $index++) {
                if ([string]$actualArray[$index] -cne [string]$expectedArray[$index]) { return $false }
            }
            return $true
        }
        'Binary' {
            $actualArray = [byte[]]$actual
            $expectedArray = [byte[]]$Expected
            if ($actualArray.Length -ne $expectedArray.Length) { return $false }
            for ($index = 0; $index -lt $actualArray.Length; $index++) {
                if ($actualArray[$index] -ne $expectedArray[$index]) { return $false }
            }
            return $true
        }
        default { return [string]$actual -ceq [string]$Expected }
    }
}

# Policy: Enable remote mailslots
# Name: Pol_EnableMailslots
# Scope: Machine
# State: Enabled
# Source: LanmanServer.admx

$isMatch = Test-RegistryValueEquals -Path 'Registry::HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows\Bowser' -Name 'EnableMailslots' -Kind 'DWord' -Expected 1
if (-not $isMatch) {
    $reasons.Add('Value mismatch: HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows\Bowser\EnableMailslots') | Out-Null
}

if ($reasons.Count -eq 0) {
    Write-Output 'Compliant'
    exit 0
}

$reasons | ForEach-Object { Write-Output $_ }
exit 1

Remediation

$ErrorActionPreference = 'Stop'

function Set-RegistryValue {
    param(
        [Parameter(Mandatory = $true)][string] $Path,
        [Parameter(Mandatory = $true)][string] $Name,
        [Parameter(Mandatory = $true)][string] $PropertyType,
        [Parameter(Mandatory = $true)][object] $Value
    )

    if (-not (Test-Path -LiteralPath $Path)) {
        New-Item -Path $Path -Force | Out-Null
    }

    New-ItemProperty -LiteralPath $Path -Name $Name -PropertyType $PropertyType -Value $Value -Force | Out-Null
}

function Remove-RegistryValue {
    param(
        [Parameter(Mandatory = $true)][string] $Path,
        [Parameter(Mandatory = $true)][string] $Name
    )

    if (Test-Path -LiteralPath $Path) {
        Remove-ItemProperty -LiteralPath $Path -Name $Name -Force -ErrorAction SilentlyContinue
    }
}

function Clear-RegistryKeyValues {
    param(
        [Parameter(Mandatory = $true)][string] $Path
    )

    if (-not (Test-Path -LiteralPath $Path)) {
        return
    }

    foreach ($propertyName in (Get-Item -LiteralPath $Path).Property) {
        Remove-ItemProperty -LiteralPath $Path -Name $propertyName -Force -ErrorAction SilentlyContinue
    }
}

# Policy: Enable remote mailslots
# Name: Pol_EnableMailslots
# Scope: Machine
# State: Enabled
# Source: LanmanServer.admx

Set-RegistryValue -Path 'Registry::HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows\Bowser' -Name 'EnableMailslots' -PropertyType 'DWord' -Value 1

History 5 retained releases

24H2 · 1.030 Sep 2024
- Added in this release.

1 later release left it unchanged.

Template

Internal name: Pol_EnableMailslots
Namespace: Microsoft.Policies.LanmanServer
Template file: LanmanServer.admx
Release: Windows 11 25H2 · 1.0 · file set de4e49983ebd651f…

Definition, editor controls and support

Definition

<policy class="Machine" displayName="$(string.Pol_EnableRemoteMailslots_Name)" explainText="$(string.Pol_EnableRemoteMailslots_Help)" key="Software\Policies\Microsoft\Windows\Bowser" name="Pol_EnableMailslots" valueName="EnableMailslots" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
      <parentCategory ref="Microsoft.Policies.LanmanServer:Cat_LanmanServer" />
      <supportedOn ref="Microsoft.Policies.LanmanServer:SUPPORTED_Windows_Server_2025_Windows_11_0" />
      <enabledValue>
        <decimal value="1" />
      </enabledValue>
      <disabledValue>
        <decimal value="0" />
      </disabledValue>
    </policy>

Editor controls

Supported platforms and category

Microsoft.Policies.LanmanServer:category:Cat_LanmanServer
<category displayName="$(string.Cat_LanmanServer)" name="Cat_LanmanServer" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
      <parentCategory ref="Microsoft.Policies.Windows:Network" />
    </category>
Microsoft.Policies.LanmanServer:definition:SUPPORTED_Windows_Server_2025_Windows_11_0
<definition displayName="$(string.SUPPORTED_Windows_Server_2025_Windows_11_0)" name="SUPPORTED_Windows_Server_2025_Windows_11_0" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
      </definition>
Microsoft.Policies.Windows:category:Network
<category displayName="$(string.Network)" explainText="$(string.Network_Help)" name="Network" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions" />
Microsoft.Policies.LanmanServer:category:Cat_LanmanServer
<category displayName="$(string.Cat_LanmanServer)" name="Cat_LanmanServer" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
      <parentCategory ref="Microsoft.Policies.Windows:Network" />
    </category>
<strings><string id="Microsoft.Policies.LanmanServer:Cat_LanmanServer">Lanman Server</string></strings>
Microsoft.Policies.LanmanServer:definition:SUPPORTED_Windows_Server_2025_Windows_11_0
<definition displayName="$(string.SUPPORTED_Windows_Server_2025_Windows_11_0)" name="SUPPORTED_Windows_Server_2025_Windows_11_0" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
      </definition>
<strings><string id="Microsoft.Policies.LanmanServer:SUPPORTED_Windows_Server_2025_Windows_11_0">At least Windows Server 2025, Windows 11</string></strings>
Microsoft.Policies.Windows:category:Network
<category displayName="$(string.Network)" explainText="$(string.Network_Help)" name="Network" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions" />
<strings><string id="Microsoft.Policies.Windows:Network">Network</string><string id="Microsoft.Policies.Windows:Network_Help">Allows configuration of components of the operating system used by a client computer to connect to a network. This includes DNS settings and Offline Files.</string></strings>