What do you mean exactly?
Are emails going to the Junk folder and you want to stop that?
If that is what you are asking I think this is a good starting point:
IMF Tune - Anti-spam extending the Exchange 2003, 2007, 2010 IMF/Content Filter - http://www.windeveloper.com/imftune/
Do you like all the junk emails go to Inbox or just few of them?
I assume you want some specific emails to go to Inbox.
You can add those sender or domain into safe list.
Also you can configure on Edge Transport server role or the Hub Transport server role.
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