Hi Odweik,
I am not aware of any specific best practices guide specifically written for Microsoft's Ex2010 product. SMSMSE 6.5 is fully supported on Exchange 2010: details on how to configure and administer SMSMSE can be found in the admin guides which came with SMSMSE.
What exactly are you trying to create a policy for controlling - spam? Content? Viruses/worms? Please do supply some additional details.
Thanks and best regards,
Mick