Created new Distribution List and hid one user from the GAL. Forced an update of the OAB so that I wouldn't have to wait the requisite up-to-24 hrs for it to update automatically. The user was still seen in the GAL and the Distribution List was only seen in All Groups, not the GAL when a user would do a look-up in Outlook for sending email. I tested by taking on of the users' Outlook out of cached mode, and then the GAL appeared correctly with the updates. I deleted the .OAB folders and the .OST file in one user's profile to see if that would clean it up permanently. That did clean it up only until the next automatic update of the OAB from the server which messed it up again. How do I resolve this permanently from the server as it is clear the server cache is messed up.