Safelist aggregation

Exchange 2007 has a feature called safelist aggregation. This compiles a list of all of your safe senders and blocked senders and then will accept mail from the safe senders (even when it looks like spam) and will reject mail from blocked senders even if it looks legitimate.

You can use this either on an Exchange 2007 Edge Transport or an Exchange 2007 Hub Transport server (if you have installed the anti-spam agents). However, you need to scan the mailboxes and update the safe list information in the Active Directory periodically using the Update-SafeList cmdlet. It must be run for each mailbox and should be run on a scheduled basis (Maybe once or twice a week? Maybe daily.) Here is the command I run:

Get-Mailbox Update-SafeList

You will get an error if a mailbox has not been moved to Exchange 2007 yet. Here is an example of the error:
[PS] V:\>get-mailbox update-safelistUpdate-SafeList : Property SafeSendersHash cannot be set on this object because it requires the object to have version 0.1 (8.0.535.0) or later. Current version of the object is 0.0 (6.5.6500.0).At line:1 char:29+ get-mailbox update-safelist <<<<