Hardening Exchange Server 2007 - Part 1: Introductory Steps

Microsoft said that Exchange Server 2007 is “Secure by Design”. Exchange 2007 was designed and developed in compliance with the Trustworthy Computing Security Development Lifecycle (TWC) which was first introduced in October 2002. Microsoft has changed a lot in this system and multiple security related improvements were built into Exchange Server 2007. Microsoft says that Exchange Server 2007 is more secure than earlier versions of Exchange.

msexchange.org's Marc Grote, has started a series of articles describing specific functions and ways of action to make your exchange 2007 environment more secure.

To the full guide

I will update as soon as the other parts will come out...