Maybe I found something that can help you

I got the same problem and I have searched and found something interesting. You must use an app called "TweakS" with this program your also able to set the messaging destination path from C:/ to E or F, whatever you want

First: You must download the newest version of TweakS and install it on C and then you open that program and go to settings and manage plugins and install the "Messaging" Plugin and open it, it will might ask you for a reboot for using this plugin, do that and open it again, it should work

And voila, your able to set the Messaging destination path

Hope it helps you

(No wonder, messaging means also e-mail stuff, theyre use the same path)
Notice: Newest version of TweakS attached
