Just a short post, but I think it might be helpful to at least a few people.
The settings in Lync can be confusing in many cases. In others, the settings are clear and obvious. I will let you decide which is which.
In this case, I was asked about the Save IM conversations in my email Conversation History folder setting. It appears that it was enabled and grayed out. The organization wanted to allow users to turn it on or off as desired. So, here are the options:
Set-CsClientPolicy –EnableIMAutoArchiving $True sets the checkbox to on and grays out the option
Set-CsClientPolicy –EnableIMAutoArchiving $False disables the checkbox and grays out the option
The solution, Set-CsClientPolicy –EnableIMAutoArchiving $Null.
Obviously, the setting has been enabled before using the $True setting.