I had recently started to experience error in Microsoft Outlook when I click a link in a HTML formatted email.
After I solved the issue with the help of a colleague, I realized that after I uninstalled Maxthon web browser, the default value of registry key "HKEY_CLASSES_ROOT \.html" was Max5.Association.HTML where it was expected to be htmlfile
Updating the registry key default value solved my problem.
Before this solution, I tried to set different web browsers as default application but did not help