I know that Exchange 2003 and 2007 can coexist. What I would like to do is install my entire Exchange 2007 environment a week ahead of moving the mailboxes. If I install Exchange 2007 (and do the domain preparation, DNS entries,etc), I'm assuming the Exchange 2007 server can sit on the network and not interfere with Exchange 2003, correct? i.e. Exchange 2007 will be present, but just won't be doing anything, and Exchange 2003 will remain active. Then when the magic move weekend comes around, I can move the mailboxes,create the MX record,and Exchange 2007 will takeover from there. Am I understanding correctly? Sorry for the dumb questions, I just want to make sure that I understand clearly. Thanks so very much for your input.

Hi, Yes Exchange 2007 can be installed in advance and doesnt interfere with your existing Exchange 2003 servers and mail flow. I would suggest thatmove some of the test users on it to understand/verifyvariousfunctionality of Exchange 2007 after installation and move the mailboxes and other tasks as per plan later. But you need to follow below article before removing Exchange 2003 server from your environment and it helps you to identify all the steps which you should follow. How to Remove the Last Legacy Exchange Server from an Organization http://technet.microsoft.com/en-us/library/bb288905(EXCHG.80).aspx Here are some of the resources for Exchange transitioning. Planning Checklist http://technet.microsoft.com/en-us/library/bb125239(EXCHG.80).aspx Best Practices for Transitioning an Exchange Organization http://technet.microsoft.com/en-us/library/bb124920(EXCHG.80).aspx How to Install Exchange 2007 in an Existing Exchange Server 2003 Organization http://technet.microsoft.com/en-us/library/bb124350(EXCHG.80).aspx