Do not prompt about Level 1 attachments when closing an item

UserNeeds changes for IntuneL_NoPromptLevel1Close

Supported on SUPPORTED_Windows7 (defined in the Windows templates)

5568.1000

What it does

This policy setting controls whether Outlook displays a warning before closing an item that contains an unsafe attachment that will be blocked when the item is re-opened.To protect users from viruses and other harmful files, Outlook uses two levels of security, designated Level 1 and Level 2, to restrict users' access to files attached to e-mail messages or other items. Outlook completely blocks access to Level 1 files by default, and requires users to save Level 2 files to disk before opening them. Potentially harmful files can be classified into these two levels by file type extension, with all other file types considered safe. If you enable this policy setting, Outlook will not display a warning when users close items with Level 1 attachments, which could cause data loss. If you disable or do not configure this policy setting, when a user closes an item to which a level 1 file has been attached, Outlook warns the user that the message contains a potentially unsafe attachment and that the user might not be able to access the attachment when opening the item later. (Such a sequence of events might occur when a user closes a draft message that they intend to resume editing at some future time.) Important: This policy setting only applies if the "Outlook Security Mode" policy setting under "Microsoft Outlook 2016\Security\Security Form Settings" is configured to "Use Outlook Security Group Policy."

What it writes

Hive: HKEY_CURRENT_USER
Registry key: software\policies\microsoft\office\16.0\outlook\security
Value name: dontpromptlevel1attachclose
When enabled: DWORD 1
When disabled: DWORD 0

Why it needs changes for Intune

Policy references a Windows supportedOn definition.
ADMX-INTUNE-WINDOWS-SUPPORTEDON-REFERENCE

Configure and deploy

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

Enabled · User · template defaults

Registry file (.reg)

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\software\policies\microsoft\office\16.0\outlook\security]
"dontpromptlevel1attachclose"=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: Do not prompt about Level 1 attachments when closing an item
# Name: L_NoPromptLevel1Close
# Scope: User
# State: Enabled
# Source: outlk16.admx

Set-RegistryValue -Path 'Registry::HKEY_CURRENT_USER\software\policies\microsoft\office\16.0\outlook\security' -Name 'dontpromptlevel1attachclose' -PropertyType 'DWord' -Value 1

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)

./User/Vendor/MSFT/Policy/Config/ADMX_outlk16/L_NoPromptLevel1Close

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>./User/Vendor/MSFT/Policy/Config/ADMX_outlk16/L_NoPromptLevel1Close</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: Do not prompt about Level 1 attachments when closing an item
# Name: L_NoPromptLevel1Close
# Scope: User
# State: Enabled
# Source: outlk16.admx

$isMatch = Test-RegistryValueEquals -Path 'Registry::HKEY_CURRENT_USER\software\policies\microsoft\office\16.0\outlook\security' -Name 'dontpromptlevel1attachclose' -Kind 'DWord' -Expected 1
if (-not $isMatch) {
    $reasons.Add('Value mismatch: HKEY_CURRENT_USER\software\policies\microsoft\office\16.0\outlook\security\dontpromptlevel1attachclose') | 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: Do not prompt about Level 1 attachments when closing an item
# Name: L_NoPromptLevel1Close
# Scope: User
# State: Enabled
# Source: outlk16.admx

Set-RegistryValue -Path 'Registry::HKEY_CURRENT_USER\software\policies\microsoft\office\16.0\outlook\security' -Name 'dontpromptlevel1attachclose' -PropertyType 'DWord' -Value 1

History 1 retained release

5568.100010 Aug 2026
- Already present in the first release ChangeIntel keeps.

Template

Internal name: L_NoPromptLevel1Close
Namespace: outlk16.Office.Microsoft.Policies.Windows
Template file: outlk16.admx
Release: Microsoft 365 Apps 5568.1000 · file set 8be05d876aae137d…

Definition, editor controls and support

Definition

<policy class="User" displayName="$(string.L_NoPromptLevel1Close)" explainText="$(string.L_NoPromptLevel1Close_Help)" key="software\policies\microsoft\office\16.0\outlook\security" name="L_NoPromptLevel1Close" valueName="dontpromptlevel1attachclose" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
      <parentCategory ref="outlk16.Office.Microsoft.Policies.Windows:L_MiscAttachmentSettings" />
      <supportedOn ref="Microsoft.Policies.Windows:SUPPORTED_Windows7" />
      <enabledValue>
        <decimal value="1" />
      </enabledValue>
      <disabledValue>
        <decimal value="0" />
      </disabledValue>
    </policy>

Editor controls

Supported platforms and category

outlk16.Office.Microsoft.Policies.Windows:category:L_MicrosoftOfficeOutlook
<category displayName="$(string.L_MicrosoftOfficeOutlook)" name="L_MicrosoftOfficeOutlook" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions" />
outlk16.Office.Microsoft.Policies.Windows:category:L_MiscAttachmentSettings
<category displayName="$(string.L_MiscAttachmentSettings)" name="L_MiscAttachmentSettings" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
      <parentCategory ref="outlk16.Office.Microsoft.Policies.Windows:L_SecurityFormsettings" />
    </category>
outlk16.Office.Microsoft.Policies.Windows:category:L_Security
<category displayName="$(string.L_Security)" name="L_Security" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
      <parentCategory ref="outlk16.Office.Microsoft.Policies.Windows:L_MicrosoftOfficeOutlook" />
    </category>
outlk16.Office.Microsoft.Policies.Windows:category:L_SecurityFormsettings
<category displayName="$(string.L_SecurityFormsettings)" name="L_SecurityFormsettings" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
      <parentCategory ref="outlk16.Office.Microsoft.Policies.Windows:L_Security" />
    </category>
outlk16.Office.Microsoft.Policies.Windows:unresolved:Microsoft.Policies.Windows:SUPPORTED_Windows7
<unresolved reference="Microsoft.Policies.Windows:SUPPORTED_Windows7" />
outlk16.Office.Microsoft.Policies.Windows:category:L_MicrosoftOfficeOutlook
<category displayName="$(string.L_MicrosoftOfficeOutlook)" name="L_MicrosoftOfficeOutlook" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions" />
<strings><string id="outlk16.Office.Microsoft.Policies.Windows:L_MicrosoftOfficeOutlook">Microsoft Outlook 2016</string></strings>
outlk16.Office.Microsoft.Policies.Windows:category:L_MiscAttachmentSettings
<category displayName="$(string.L_MiscAttachmentSettings)" name="L_MiscAttachmentSettings" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
      <parentCategory ref="outlk16.Office.Microsoft.Policies.Windows:L_SecurityFormsettings" />
    </category>
<strings><string id="outlk16.Office.Microsoft.Policies.Windows:L_MiscAttachmentSettings">Attachment Security</string></strings>
outlk16.Office.Microsoft.Policies.Windows:category:L_Security
<category displayName="$(string.L_Security)" name="L_Security" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
      <parentCategory ref="outlk16.Office.Microsoft.Policies.Windows:L_MicrosoftOfficeOutlook" />
    </category>
<strings><string id="outlk16.Office.Microsoft.Policies.Windows:L_Security">Security</string></strings>
outlk16.Office.Microsoft.Policies.Windows:category:L_SecurityFormsettings
<category displayName="$(string.L_SecurityFormsettings)" name="L_SecurityFormsettings" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
      <parentCategory ref="outlk16.Office.Microsoft.Policies.Windows:L_Security" />
    </category>
<strings><string id="outlk16.Office.Microsoft.Policies.Windows:L_SecurityFormsettings">Security Form Settings</string></strings>