With Microsoft Project Server 2010 the outlook add-in we used in 2007 version of SharePoint to synchronize tasks are retired. Now Project Server 2010 synchronize tasks directly with Exchange Server. You need a Exchange Server 2007 with minimum SP2. On details of how to configure it please refer to – http://technet.microsoft.com/en-us/library/ee782548.aspx
However if your customers are using office 2007 there is an easy way out. All you have to do is get your hands on the 2007 version of project server-outlook add-in and install that in the client computer. If you don’t want to go through the trouble of setting up a project server 2007 you can download the add-in at – http://cid-15a85081c9b1419f.office.live.com/self.aspx/Public/SharePoint%202010/PsOlkAddin.zip
