{ 
  Here is some code I successfully used te determine 
  the DEFAULT mailaccount, which is used in 
  Outlook Express, to send outgoing mail via SMTP. 
} 

procedure TForm1.ReadRegistryDefaults; 
var 
  Registry: TRegistry; 
  AccountStr: string; 
begin 
  Registry := TRegistry.Create; 
  try 
    Registry.RootKey := hkey_CURRENT_USER; 
    if Registry.OpenKey('software\microsoft\internet account manager', False) then  {} 
    begin 
      AccountStr := Registry.ReadString('default mail account'); 
      Registry.CloseKey; 
      if (AccountStr <> '') then 
        if Registry.OpenKey('software\microsoft\internet account manager\accounts\' + 
          AccountStr, False) then  {} 
        begin 
          Edit_Server.Text  := Registry.ReadString('SMTP Server'); 
          Edit_Account.Text := Registry.ReadString('SMTP Email Address'); 
          Registry.CloseKey; 
        end; 
    end; 
  finally 
    Registry.Free; 
  end; 
end;