I am planning to depoly a new Exchange 2007 solution in my enviroment, which will be running on Hyper-V. It will host approx 200 low/medium use mailboxes. Access will be via Outlook 2007 cached mode, and a few OWA and ActiveSync Mobile Push connections.I have built a ms vm running Server 2008 Std and Exchange 2007 Std, all roles installed. Everything was built with standard options. Currently I recieve and send directly over DNS, but this will soon be changed through a provider such as postini or C&W. And as such firewall will be closed down.I have also purchased an extended SSL cert to run on my owa page.I am wondering how secure this solution is, are there any best practise docs regarding tightning the security on Exch2007 1 server solutions, what steps can I implement to ensure this solution is as secure as possible?Any help you can offer would be much appreciated.

You have to examine security from multiple dimensions, but the most common next step for an installation such as yours usually involves adding levels of seperation from the Exchange server and the internet. This is because of multiple reasons; two of which are IIS and SMTP type attacks. Something like ISA 2006 and an Edge transport server will address those issues respectivly.Your question provokes a discussion, not a simple answer, so I suggest you review the following links for further detail and then repost more specific questions so that we can better assist.Hardening Exchange Server 2007 - Part 1: Introductory StepsWebcast TechNet: Hardening Exchange 2007Top 5 Exchange Server 2007 Security Best Practices Mike Crowley A+, Network+, Security+, MCT, MCSE, MCTS, MCITP: Enterprise Administrator / Messaging Administrator