Looks like the SPF entry is incorrect. Post your master.cf and main.cf.
I'm not sure if the script works with Exchange 2010, but you can use the look_ahead feature as an alternate. You cannot implement both, so it's either relay_recipient hash or look_ahead. If you plan to use relay_recipients hash, then you should disable look_ahead. Give this page a look: http://thelowedown.wordpress.com/200...y-to-exchange/
Otherwise, setup main.cf as described under the postfix section in the guide and enable look_ahead.
Read through the guide carefully, as some things are optional. That is up to you to install should you need those features.