Uninstalled Avast browser and Outlook now restricts/rejects all email links

Avast Free Antivirus / Premium Security
1

Since uninstalling AVAST browser I have a major problem with my Outlook 2010. Every email link I click on gives the message
‘This operation has been cancelled due to restrictions in effect on this computer. Please contact your systems administrator’.
I am the systems administrator, but did not directly change any settings to create this problem with Outlook 2010.
I have spent 3 days researching and applying supposed fixes for this problem. Most agree this problem occurs when a browser that is still configured as the default browser is uninstalled. None of the fixes have worked. And despite the uninstall, the registry still contains many references to and settings for Avast_Secure_Browser and AvastBrowser.exe

The last program update to the Avast free Antivirus (to 20.3.405) installed the AVAST Secure browser and made it the default. I did not notice this option so missed cancelling it. Mea Culpa.
I already have Brave, Firefox, Edge, Chrome and Opera browsers.
Following theAvast browser install, the Opera and Brave browsers did not recognise any certificate and prompted me to accept or reject every page. I eventually managed to research and fix this annoying problem.
I did not need another browser so uninstalled the AVAST Secure browser, but did not change the default browser before doing so.
Since then I have this major problem with my Outlook

Can anyone suggest how to fix this short of replacing Avast as my antivirus or re-installing Outlook. I have used this for a few years now and am otherwise happy with the program.

Best Regards

Phil

2

See if this (Uninstall via removal tool) helps: https://support.avast.com/en-ww/article/30

3

You may have fixed this already but this one change to the registry fixed it for me.

(from https://support.microsoft.com/en-us/help/310049/hyperlinks-are-not-working-in-outlook)
…
Step 3: Verify that the String (Default) value of the “HKEY_CLASSES_ROOT .html” key is “htmlfile”

Select Start > Run.
In the Open box, type regedit, and then select OK.
Locate, and then click the following registry subkey:HKEY_CLASSES_ROOT .html
Make sure that the value of the String (Default) is “htmlfile”. If it’s not “htmlfile”, right-click (Default), select Modify, input htmlfile in the Value data box, and then select OK.

Exit Registry Editor.