If for any reasons, you want to manually update your Forefront Protection 2010 for Exchange Server and Forefront Protection 2010 for SharePoint scan engines. "Well, you can do it, but it's a long process to provide guidance here to those of you who wish to manually update FPE/FPSP scan engines and definitions as part of your Forefront Protection defense strategies. But, Microsoft has provided a comprehensive set of instructions via Knowledge Base article that describes how to manually update the scan engines in Forefront Protection for Exchange Server or Forefront Protection for SharePoint. You may have to do this if you experience issues with the updates. Article also describes how to update scan engines from a computer that doesn't have Forefront Protection server security products installed.
More Info: KB2292741