We are in the process of migrating a small office to Exchange 2010 then 2013 from 2003. Our current 2003 server has all roles on a single box and so will our Exchange 2010 server (and 2013 after 2010). We have Exchange 2010 installed into our domain and it is part of our current Exchange organization.
My question is about our public DNS. For the new Exchange 2010 server we need a new A record (which will be nat'd to our internal number space) and should we assign a secondary MX record to the new Exchange 2010 server with a weight of 20? Our current Exchange 2003 server has an MX record with a weight of 10.
Is this the way to go? I want to be able to receive mail on Exchange 2003 and on migrated mailboxes on our 2010 server and keep both live until all mailboxes are moved.
Currently we don't have any mailboxes moved yet.
Thank you for any assistance.