I guess I'm doing the opposite of an in-place upgrade (which I see is not possible from 2003 -> 2010 regardless) so my only option is to install exchange 2010 in an existing exchange 2003 organization on different hardware which is good thing in my case. I will be installing all roles on one server. The 2k3 environment is only one server (about 100 users). I've never done this before and I'm wondering if I'll need 3rd party software to move the resources from server to server or if anyone recommends a software to make it easier. I've used CodeTwo Exchange migration to move from one 2010 to another 2010 but that is it. If not will the 2k3 servers show up in the 2010 EMC and can I migrate mailboxes into the 2010 databases as if I was moving users between mailbox databases in 2010?
I'm reading that when I install Exchange 2010 it will see the existing environment and go into what is called coexistence mode. I assume this is all automatic with install and with this it creates the security groups needed to grant the permission to allow the 2k3 servers to send to the new 2010. Also, a two-way routing group between the two
The only resource I'm using right now is this TechNet article - http://technet.microsoft.com/en-us/library/aa998186(v=exchg.141).aspx
Also, I'm curious if I need to get and outage window for any of the steps along the way. Is any downtime required throughout the upgrade process. Thank you!!!