Right now we have multiple sites with their own CAS/HUB/MB servers and a Microsoft TMG server in the DMZ for OWA, Active Sync & Outlook Anywhere. One site has a CAS array with 2 mailbox servers, another site just has a single CAS server and a mailbox server and the other 4 sites have a single CAS/HUB/MB server. We are a single domain.
We want to centralize at our main datacenter and put in 2 CAS Servers creating a new CAS Array and using Netscaler for load balancing and HTTPS traffic. We are then going to build 4 new Mailbox servers and implement DAG. Once that is completed we will start moving our users mailboxes to the new mailbox servers. Our goal is to centralize and increase mailbox limits, enable retention periods and eliminate PST files on our file servers.
My question is can build all of this in our existing Exchange organization without breaking anything and as we get mailboxes moved over decommission the old Exchange servers. I should mention we have a total of 2000 mailboxes and about 1000 of them are actual users.
Any input and guidenace would be appreciated.