Outlook Won’t Open Links – Canceled Due to Restrictions

I had a customer call me with a strange issue. They had had a bit of an “incident” with a virus, but they had installed virus protection and gotten things cleaned up. However, they had a new issue now. Every time they clicked on a link in their email in Outlook, they would just get an error message and the links would not open.

The error message they were receiving was:
This operation has been canceled due to restrictions in effect on this computer. Please contact your system administrator.

They thought it was related to the virus incident or the installation of the anti-virus software. Upon first hearing about the issue, I initially thought it was an issue in Outlook. Turns out, it was an issue with Windows. They were running Windows 10, and they used to have Firefox as their default browser. When they had the issue with the virus, they uninstalled Firefox to try to help clean things up. Windows 10, however, did not recognize that Firefox was no longer the default browser, leading to Windows not knowing how to open links in Outlooks.

The first place I checked was in the Default Apps settings. To get to this, I clicked on the Start button, then on Settings, then on Apps, and then on Default Apps. I then scrolled down to Browser, and made sure Edge was selected here instead of Firefox. This, however, did not solve the problem.

So, I knew I had to dig into the registry. I opened up the search box, entered “run”, and then in the run app, I entered “regedit”. I then navigated to HKEY_CURRENT_USER\Software\Classes and found the .html entry. I then right-clicked on Default in the Name column and chose “Modify”. I changed “FirefoxHTML” to “htmlfile”. I did the same for the Default entries for .htm, shtml, .xht, .xhtml, and .web. I closed regedit and Outlook, reopened Outlook, and now the links within the emails worked again.