Outlook raises an error on window.external

[Krzysztof Żelechowski]

Ping from
<https://poczta.wp.pl/uwierzytelnianie/?list=4E5FC9GD0O14F3MD5AJ10A58B1JE8B47DIA4CC42S&ticaid=16f53> (in Polish).
Summary: if script code on an HTML page that Outlook tries to display tries
to reference window.external, the reference causes a run-time error.