If you have to whitelist an email address in Exchange 2010 antispam, either as part of SBS 2011, on an edge transport server, or any server with the edge transport server role installed, there seems to be nowhere to do it.
A simple solution is to use a transport rule to set the SCL (spam confidence level) of any message from the sender to zero.
You can click on the images below for a larger version.
Open the Exchange Management Console (EMC) and go to the Hub Transport Role
In the action pane on the right client on ‘New Transport Rule’
Give the rule a useful name and description
Select ‘from people’
Choose ‘external address’
Enter the address you want to whitelist.
Click Ok to add the address. Repeat this for any additional addresses.
Click next to move onto the next step in the rule
Tick ‘set the spam confidence level’ (SCL). It will default to 0 so no need to change this.
Leave any exceptions blank, unless you need to add them.
Click on ‘new’ to create the rule.
Done! Now any emails from that address will not be marked as spam.
This screenshots will be slightly different but the process should be identical on Exchange 2007.