The parameters used by the Microsoft Mailapplication provided with Windows NT appear under this subkey:
HKEY_CURRENT_USER\Software\Microsoft\Mail
Many of the entries in the subkeys of this key have default values and won't be present. To change the appearance and behavior of the Mail application, use the Mail menu commands instead of editing the Mail entries directly. Some of the options that you specify in the Mail application are stored in your mail message file (.MMF) instead of the Mail Registry entries.
These keys are created in HKEY_CURRENT_USER when you first run Mail. If your system previously contained a Windows for MS-DOS version of MSMAIL.INI, its contents are migrated to the Registry when you first run Mail under Windows NT.