I'm trying to transit our exchange 2003 to 2010. My question is that can I just install Exchange CAS role first without installing mailbox and Hub role? How long can I use CAS role without installing/adding mailbox 2010 and hub role? If I install and redirect OWA and OMA to new CAS server will it start working without adding 2010 mailbox? And, internal mail clients will start accessing their 2003 mailbox via new CAS 2010 server? I've installed all the prerequisites to install exchange 2010. The other question is I will have two separate server and what's the best way to install Hub role server with mailbox server or with CAS role server? Thanks, John

In theory yes but something I haven't tried. Don't think you redirect OMA, you can use OMA with SP2 but that will require a mailbox on 2010. The clients can use 2010 but if the mailbox is on 2003 then as far as I know they wont. They still connect to the backend 2003 server.Sukh

My question is that can I just install Exchange CAS role first without installing mailbox and Hub role? Yes. That's the first E2K10 role you would normally install in a E2K3 -> E2K10 transition scenario. How long can I use CAS role without installing/adding mailbox 2010 and hub role? For quite a while. Even as long as you want. But you will need to adjust some DNS records (create a legacy record so E2K10 can redirect clients with a mailbox on a E2K3 BE server to the E2K3 FE server). There is also a legacy URL to configure. If I install and redirect OWA and OMA to new CAS server will it start working without adding 2010 mailbox? Yes for OWA. Not sure about OMA. And, internal mail clients will start accessing their 2003 mailbox via new CAS 2010 server? The CAS will redirect clients with mailboxes on a E2K3 mailbox server to a E2K3 FE server. You need to keep your E2K3 FE server until all mailboxes are moved to the E2K10 server. The E2K10 CAS cannot provide (direct) access to a mailbox on a E2K3 server by itself. The other question is I will have two separate server and what's the best way to install Hub role server with mailbox server or with CAS role server? I would consider installing all 3 roles on both servers. That would allow you to configure a DAG and enjoy some sort of redundancy for all roles, except the CAS (you cannot have both DAG and CAS NLB on the same servers). Note that none (or not much) of the above will configure itself. You need to read the documentation carefully. Please mark as helpful if you find my contribution useful or as an answer if it does answer your question. That will encourage me - and others - to take time out to help you.

Hi Quote: My question is that can I just install Exchange CAS role first without installing mailbox and Hub role? Answer : Yes, you can. Quote: If I install and redirect OWA and OMA to new CAS server will it start working without adding 2010 mailbox? Answer: OWA: cas 2010 will redirect web page to exchange 2003 if the mailboxes are on exchange 2003. OMA: SUKHs answer is perfect. Quote: The other question is I will have two separate server and what's the best way to install Hub role server with mailbox server or with CAS role server? Answer: you had better install hub role with cas role. Mailbox role will consume all memory,cpu usage and capacity. TechNet Subscriber Support in forum If you have any feedback on our support, please contact tngfb@microsoft.com Terence Yu TechNet Community Support