Randomly in the sense of "without their knowledge". Unless you have access to both mailboxes it isn't something you can do.
We have staff that insist they used to be able to access their files at home. It isn't true.
Just grabbed the free version of "Advanced Installer" to make some mst files... Changed reboot to suppressed and autoupdate to 0.
Lets see if this works... [Worked fine raw.]