KB ID 0000352 Dtd 11/11/10
Note: This Procedure is the same for Exchange 2007.
You are having a problem with spam, the Exchange agents are no replacement for a proper AntiSpam solution, but they are better than nothing. By default they don't install, unless you are installing an "Exchange Edge Transport Server". For most SMB client that's not an option so there's nothing to stop you installing the options on your "Stand Alone" Exchange box.
Note: You can also enable and disable the Anti-Spam features with the following poweshell commands (you still need to restart the transport service afterwards).
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