Use UTF-8 for mailto links: registry value UTF8EncodingComputerHKLM\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\Protocols\Mailto

Policy ID: ControlPanel_SendUTF8Query
Scope: Computer Configuration, User Configuration
Supported on: At least Internet Explorer 7.0
Source: Administrative Templates (.admx) for Windows 11 2026 Update (26H2) (version 1.0)
Category: Windows Components › Internet Explorer › Internet Control Panel

Registry

UTF8Encoding

REG_DWORDComputerUser

…\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\Protocols\MailtoHKLM\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\Protocols\Mailto Current key
HKCU\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\Protocols\Mailto

Enabled value: 1
Disabled value: 0

Apply with .reg · CMD · PowerShell

ComputerMachine-wide setting

.reg

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\Protocols\Mailto]

; Options (use only one)
; Enabled
"UTF8Encoding"=dword:00000001
; Disabled
"UTF8Encoding"=dword:00000000

CMD

:: Options (use only one)

:: Enabled
reg add "HKLM\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\Protocols\Mailto" /v "UTF8Encoding" /t REG_DWORD /d 1 /f
:: Disabled
reg add "HKLM\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\Protocols\Mailto" /v "UTF8Encoding" /t REG_DWORD /d 0 /f

PowerShell

# Common: create the key
New-Item -Path 'HKLM:\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\Protocols\Mailto' -Force | Out-Null

# Options (use only one)
# Enabled
New-ItemProperty -Path 'HKLM:\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\Protocols\Mailto' -Name 'UTF8Encoding' -PropertyType DWord -Value 1 -Force | Out-Null
# Disabled
New-ItemProperty -Path 'HKLM:\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\Protocols\Mailto' -Name 'UTF8Encoding' -PropertyType DWord -Value 0 -Force | Out-Null

UserPer-account setting

.reg

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\Protocols\Mailto]

; Options (use only one)
; Enabled
"UTF8Encoding"=dword:00000001
; Disabled
"UTF8Encoding"=dword:00000000

CMD

:: Options (use only one)

:: Enabled
reg add "HKCU\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\Protocols\Mailto" /v "UTF8Encoding" /t REG_DWORD /d 1 /f
:: Disabled
reg add "HKCU\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\Protocols\Mailto" /v "UTF8Encoding" /t REG_DWORD /d 0 /f

PowerShell

# Common: create the key
New-Item -Path 'HKCU:\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\Protocols\Mailto' -Force | Out-Null

# Options (use only one)
# Enabled
New-ItemProperty -Path 'HKCU:\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\Protocols\Mailto' -Name 'UTF8Encoding' -PropertyType DWord -Value 1 -Force | Out-Null
# Disabled
New-ItemProperty -Path 'HKCU:\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\Protocols\Mailto' -Name 'UTF8Encoding' -PropertyType DWord -Value 0 -Force | Out-Null