If you use Outlook’s Home Page feature and installed October 2017’s current updates, you might experience this feature is suddenly gone (due to security reasons, according to Microsoft).
However, this feature is very useful to display web pages in Outlook. This can e.g. be a central mail archive integration like MailPiler, or any other web content.
Fortunately, you can re-enable the feature via registry:
No system reboot is needed, just restart Outlook.
For further details have a look here, there are more detailed reg keys available.