Starting with Exchange 2007, installation of the current version of Office Filter Packs is a prerequisite. For Exchange 2007 and Exchange 2010 RTM, the pre-req was 2007 Office System Converter: Microsoft Filter Pack. In Exchange 2010 SP1, this was updated to Office 2010 Filter Packs. The filters are used by Exchange Search to index email attachments on Mailbox servers and by the transport rules agent to scan attachments on transport servers. The filters are also important for discovery searches in Exchange 2010 – Multi-Mailbox Search uses content indexes generated by Exchange Search.
In Exchange 2010 RTM and Exchange 2007, you need to register the IFilters with Exchange Search (for Exchange 2007, see 'KB 944516 How to register Filter Pack IFilters with Exchange Server 2007'). In Exchange 2010 SP1, IFilters included in the Office 2010 Filter Pack are automatically registered by Exchange Setup. You must register any third-party filters you install.
An updated filter pack, Service Pack 1 for Microsoft Office Filter Pack 2010 (KB2460041) 64-bit Edition is now available on Download Center. The Filter Pack has been tested with Exchange 2010 and Exchange 2007. The updated filter pack doesn’t have any fixes or updates that impact Exchange scenarios or functionality. If you have the RTM version of Office 2010 filter packs installed, you can update it but it’s not required. For new installs, we recommend going with the current versions.
Credits to Bharat Suneja