Exchange 2010 – Why do I need an earlier product version?

Having an interesting conversation today with a customer regarding a migration.  Exchange 2010 is getting considerable interest but before anyone considers a deployment it should be validated a previous version of Exchange isn’t needed.  Why you may ask?  If you require Exchange 2003 or Exchange 2007 in your environment you cannot install these previous versions of Exchange unless you have installed them PRIOR to installing Exchange 2010. 

 Got you thinking now haven’t I?  What scenarios would you need to install previous versions of Exchange Server prior to Exchange Server 2010 I presume is your first question.  Well there are certain cases where Microsoft tools (the transporter suite) or 3rd party tools/software does not yet or will not work with Exchange Server 2010. In these scenarios, you may need to install a previous version of Exchange Server such and 2003 or 2007 to coincide with Exchange Server 2010. 

In my conversation today it was a Lotus migration.  If you need to migrate from Lotus Domino and want to leverage the Microsoft Transporter suite an Exchange 2007 server needs installed since there will be no version developed for Exchange Server 2010.  Certainly the Transporter suite is critical if you want to have Interorg free/busy calendar information.  I will post more when the 3rd party tools have had further product releases but for now give careful consideration when deploying Exchange.