Co-existance and Migration Email Flow

Hi,

I have Exchange 2010 DAG Multi Role with 2 Servers , I am planning to Introduce Exchange 2013 in my Organization ,  I will create a new DAG on Exchange 2013 Multi Role Server . My Question is about email flow.

1- Right After installing Exchange DAG , Email flow will remain same to Exchange 2010 or it will be changed to Exchange 2013 ?  

2- During Coexistence Mail Flow will be routed to Exchange 2013 even from external and proxy traffic to Exchange 2010. ?   

3- Do i need to change anything on configuration level on Exchange 2010.

Regards

Usman Ghani           

Usman Ghani - MCITP Exchange 2010