Philip Richardson posted about this a long time ago, but his post has actually not available any more. This is a great hack to make an end user's life a lot easier. By default the Outlook Most Recently Used (MRU) list is set to 7 items. A lot of users I talk to like it to be longer. And there is a simple registry modification that can be made to increase (or decrease) the length of the list.
Add the following reg key to the client machine that wants the length of the MRU changed:
Value Name: MaxRegardingObjectListCount
Then just put the number you want displayed (in Decimal format) and you're all set. You will most likely need to close your Outlook and reopen it for the changes to take effect.
Also, please note that you should know what you are doing when you are changing the registry (be careful), as if you modify it incorrectly it could make your application, or computer not work properly any more. Modifying the registry is done at your own risk.
But that should get you going. Enjoy,
Dynamic Methods Inc.