Hi,
we are in process of upgrading existing Exchange 2007 to exchange 2013. follwing the below MS article:
http://technet.microsoft.com/en-us/library/jj898582(v=exchg.150).aspx
In the below sction
Step 7: Create a legacy host name:
In our case we are going to map the ip of legacy exchange 2007 external url ip to Exchange 2013 external url.
in this case in which dns server internal or external should I put the legacy.compay.com record which pointing to my legacy Exchange 2007 server.
let me know How exchange 2013 handle incoming webapp request if the user is in the legacy exchange 2007 server.