We've installed an Exchange 2010 server into what was a 2003 domain. Managed to migrate all the accounts, and even deal with a number of relatively small headaches in the process. Now we're ready to complete the cutover. But the 2003 server is still the default path for traffic in and out of Exchange. Mail heading to the Internet still goes to the 2003 server, before getting sent off to our SonicWALL mail device. Inbound mail still goes through the 2003 server to get into Exchange. (Yes, part of that will require that I make changes in the SonicWALL, but beyond that - if I switch it there, will that enable mail to start coming directly in, or is that going to screw me up?)
What more do I need to do?
Also, Exchange 2010 seems to function a LOT slower than 2003 did. Is this a related issue? Is there something else involved?
Also you need to configure send connectors on 2010 server for outbound delivery and delete SMTP connector on 2003 server
As long as RGC is there, your mail flow should work fine between 2003 and 2010
In case of sonic wall you need to change all references from 2003 to 2010 server
Lastly in order to remove exchange 2003 server completely from 2010 organization, follow step by step article