Hi,
The problem is that "Since the traditional methods for accessing message source in Outlook are not currently providing the desired functionality without opening the email" is not true.
The traditional methods have been removed.
Regarding #1 -
I can't install extra tools -nor should I need to - to provide functionality that was, and should still be, provided out of the box with Outlook. Also, it appears from sources that the changes made to outlook render this add-in non-functional.
Regarding #2 -
The traditional method (up until recently) was to right-click on the message in the message list and select "view source" . This let you look at the headers and the html behind the message to see if links were dangerous. This functionality is what has been REMOVED from current version.
Regarding #3 - this is a standard setting, but forcing us to open an email to check its validity is a process akin to checking if a gun is loaded by pointing it at your head and pulling the trigger...
Regarding #4 -
Security best practice is to inspect message source before opening the message so that you can see if the sender has tried to hide malicious links using any of a number of techniques.