Something has been installed on this one particular system at some point in time related to HubSpot which is a marketing platform. From a purely logical standpoint - it would not be a generic issue related to Outlook since all of your other users would have
the same issue (as would the rest of the world).
General information about what HubSpot is all about
The #1 Marketing Platform
http://www.hubspot.com/
When simply going to the domain "cdn2.hubspot.net" it comes back with <The HubSpot account associated with the domain "cdn2.hubspot.net" has expired> which no doubt is related to the balance of the UNC blacked out
in the screenshot. Would suggest (1) talking to this user to see what has been installed on the system (2) checking all programs installed via the Control Panel to see if there is anything related to HubSpot such as "Signals by HubSpot" etc.
Another relevant question that I should have asked - "Is this something that was presented from Day one of Outlook use or is this something that has started to show recently?