CLASS vs CLASS_A vs CLASS_W

Question

Hello,
Many of the Outlook properties have 3 versions: CLASS, CLASS_A and CLASS_W

Any idea the difference?

And there are 2 sets of message class properties: PR_MESSAGE_CLASS vs PR_ORIG_MESSAGE_CLASS which am not sure about the difference!

To get a simple message class we have at least 6 different properties :(

• Found these:
• PR_MESSAGE_CLASS vs PR_ORIG_MESSAGE_CLASS
• While still don't know the difference :(