Exchange Unicode Mode - Ignore OST Format
Verified with Microsoft 365/Office 5568.1000 — updated on September 4, 2026
Supported on: At least Windows Server 2008 R2 or Windows 7
Path in the GPO console
User Configuration\Administrative Templates\Microsoft Outlook 2016\Account Settings\Exchange Description
This policy setting allows you to specify whether existing OST format determines the mailbox mode. If you enable this policy setting, you may choose one of these options: * OST Format determines mode: the format of the user's OST file will be used to determine whether to run in Unicode or ANSI mode. * Create new OST if format doesn't match mode: create a new OST file if needed. * Prompt to create new OST if format doesn't match mode If you disable or do not configure this policy setting, you will not be able to specify whether existing OST format determines the mailbox mode. This policy is ignored if PreferANSI is not set and the OST is enabled but either does not exist or is a Unicode OST, because it would be impossible for the user to create an ANSI OST.
Registry
HKCU
software\policies\microsoft\office\16.0\outlook\emsp 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: Exchange Unicode Mode - Ignore OST Format
; State: Enabled
; Supported on: At least Windows Server 2008 R2 or Windows 7
[HKEY_CURRENT_USER\software\policies\microsoft\office\16.0\outlook\emsp]
"ignoreostformat"=dword:00000000More formats (PowerShell, Intune, SCCM)
PowerShell
# Exported from gporais.com
# Policy: Exchange Unicode Mode - Ignore OST Format
# State: Enabled
# Supported on: At least Windows Server 2008 R2 or Windows 7
# Warning: In SYSTEM context (the Intune default), HKCU targets the SYSTEM profile. Run this script using the logged-on credentials.
$path = 'HKCU:\software\policies\microsoft\office\16.0\outlook\emsp'
New-Item -Path $path -Force | Out-Null
Set-ItemProperty -Path $path -Name 'ignoreostformat' -Value 0 -Type DWordIntune XML
No direct Policy CSP / OMA-URI mapping for this policy. Use the Intune Remediation tab, or ingest the ADMX in Intune.Intune Remediation
# === Detection script ===
# Exported from gporais.com
# Policy: Exchange Unicode Mode - Ignore OST Format
# State: Enabled
# Supported on: At least Windows Server 2008 R2 or Windows 7
# Warning: In SYSTEM context (the Intune default), HKCU targets the SYSTEM profile. Run this script using the logged-on credentials.
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
}
$checks = @(
(Test-RegistryValue -Path 'HKCU:\software\policies\microsoft\office\16.0\outlook\emsp' -Name 'ignoreostformat' -Expected 0 -Kind DWord)
)
if ($checks -notcontains $false) {
Write-Output 'Compliant'
exit 0
}
Write-Output 'Non-compliant'
exit 1
# === Remediation script ===
# Exported from gporais.com
# Policy: Exchange Unicode Mode - Ignore OST Format
# State: Enabled
# Supported on: At least Windows Server 2008 R2 or Windows 7
# Warning: In SYSTEM context (the Intune default), HKCU targets the SYSTEM profile. Run this script using the logged-on credentials.
$path = 'HKCU:\software\policies\microsoft\office\16.0\outlook\emsp'
New-Item -Path $path -Force | Out-Null
Set-ItemProperty -Path $path -Name 'ignoreostformat' -Value 0 -Type DWordSCCM scripts
# Exported from gporais.com
# Policy: Exchange Unicode Mode - Ignore OST Format
# State: Enabled
# Supported on: At least Windows Server 2008 R2 or Windows 7
# 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: Exchange Unicode Mode - Ignore OST Format
# State: Enabled
# Supported on: At least Windows Server 2008 R2 or Windows 7
# Warning: In SYSTEM context (the Intune default), HKCU targets the SYSTEM profile. Run this script using the logged-on credentials.
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
}
$checks = @(
(Test-RegistryValue -Path 'HKCU:\software\policies\microsoft\office\16.0\outlook\emsp' -Name 'ignoreostformat' -Expected 0 -Kind DWord)
)
if ($checks -notcontains $false) {
Write-Output 'Compliant'
exit 0
}
Write-Output 'Non-compliant'
exit 1
# === Remediation script ===
# Exported from gporais.com
# Policy: Exchange Unicode Mode - Ignore OST Format
# State: Enabled
# Supported on: At least Windows Server 2008 R2 or Windows 7
# Warning: In SYSTEM context (the Intune default), HKCU targets the SYSTEM profile. Run this script using the logged-on credentials.
$path = 'HKCU:\software\policies\microsoft\office\16.0\outlook\emsp'
New-Item -Path $path -Force | Out-Null
Set-ItemProperty -Path $path -Name 'ignoreostformat' -Value 0 -Type DWordBuilding a multi-setting collection? Add this setting and generate combined .reg / PowerShell / GPO scripts.