MSExchangeTeam blogged about a new feature in Exchange Server 2010: Moderation using Transport Rules.
Let's say you have a business process that requires the approval of two different people. Well, with moderationand transport rules, you can automate that process with Exchange 2010 and Outlook 2010.
If we created a single transport rule with moderation as the action, and added these two recipients, the message could be approved by either [email protected] or [email protected] (just like approving a message sent to a moderated group). However, in this case we want approval from both. To do that, we need to create two rules. The order in which the rules are processed specifies who has to approve the message first.
Check this out at the source: http://msexchangeteam.com/archive/2009/12/16/453607.aspx