http://blogs.technet.com/dst2007/archive/2007/03/01/do-i-need-cdo-patch-for-exchange-5-5-if-i-decide-to-run-outlook-tool-from-client.aspxQ: Do I need CDO patch for Exchange 5.5 if I decide to run outlook tool from client A: Exchange Server 5.5 is no longer a supported product, as described at http://support.microsoft.com /lifecycle/?p1=1776 . Microsoft’s Lifecycle policy can be found aten-USCommunityServer 2.1 SP1 (Build: 61025.2)