So outlook has stopped opening links or attachments and there have been no changes in the trust center and no recent windows updates…. Open Regedit and check the following key. “HKEY_CLASSES_ROOT \.html”
Verify that the String (Default) value of the “HKEY_CLASSES_ROOT \.html”
key is “htmlfile” (Not something like ProgID)
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.