Hide your email address on the sign-in screen — via Microsoft Learn

Group Policy

Open gpedit.msc (Pro, Enterprise and Education only) and go to:

Computer Configuration > Administrative Templates > System > Logon > Block user from showing account details on sign-in

Registry equivalent

Double-click a .reg file and confirm to merge it. Right-click → Edit first if you want to read it, which is always a good idea with any .reg file from the internet.

Apply

Windows Registry Editor Version 5.00

; Oddbyte.Me: Hide your email address on the sign-in screen

[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\System]
"BlockUserFromShowingAccountDetailsOnSignin"=dword:00000001

Undo

Windows Registry Editor Version 5.00

; Oddbyte.Me: undo Hide your email address on the sign-in screen

[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\System]
"BlockUserFromShowingAccountDetailsOnSignin"=-

Same thing from a command prompt

Run in an administrator Command Prompt or Terminal.

reg add "HKLM\SOFTWARE\Policies\Microsoft\Windows\System" /v "BlockUserFromShowingAccountDetailsOnSignin" /t REG_DWORD /d 1 /f

Undo:

reg delete "HKLM\SOFTWARE\Policies\Microsoft\Windows\System" /v "BlockUserFromShowingAccountDetailsOnSignin" /f

Microsoft's security baseline checks for this value set to 1. Without the policy, each user can choose whether account details show (Settings → Accounts → Sign-in options).