Exchange 2003 /2010 Co-existence plus 2010 migration to new hardware

Question

Hi,
Here is our current scenario;
Exchange 2003/2010 co-existence. This has been running perfectly for a couple of months now.
Exchange 2003 - exch1.domain.lan
Exchange 2010 (SP3) - exch2.domain.lan (local domain name)  /  mail.domain.com.au (external domain name)
ActiveSync, autodiscover, legacy etc are all working. Our UAC certificate from GoDaddy has all the required names for exch2 - except it doesn't have the local domain name as they don't allow certificates with that anymore. I've configured all the required
services to be the external domain name and am running split DNS.
The first Exchange 2010 server I installed was lower spec'd and only has about 25 users on it. I now need to install a second Exchange 2010 server (exch3.domain.local), which is properly spec'd and will host the entire company. I won't be running DAG as
I need to repurpose the first Exchange 2010 server once it's removed.
My high level questions are;
1) Should I migrate everyone off Exchange 2003 onto Exchange 2010, decommission the 2003 server, and then install the second 2010 server? OR
2) Should I install the second Exchange 2010 server, migrate everyone from the first Exchange 2010 server, decommission that one, then do the migration from 2003 to 2010?
OR does it matter which way I do it?
I've read what I can find about installing the second Exchange 2010 server into the organisation. It seems to be pretty simple at first. Just install Exchange 2010 with HT, mailbox and CAS roles which will automatically configure it into the same Exchange
organisation.
1) Do I configure CAS to be externally facing right from the get go or do I do that later?
2) As soon as I install the second Exchange 2010 server, will I encounter any mail flow problems? Will mail be trying to flow out of the second Exchange 2010 server as well as the first?
In regards to SSL, so obviously the second Exchange 2010 server will have a different local domain name than the first, but ultimately, I want it to have the same external domain name, eg mail.domain.com.au. As my certificate doesn't contain any local domain
names, can I export the certificate from exch1 and import it into exch2, or should I just generate a new CSR from exch2 and get GoDaddy to reissue it?
OR should I look at creating a CAS Array from exch1 and adding exch2 to it. (I don't fully understand the workings of this at the moment).
Any guidance on the above is helpful.
Thanks.
Steve

Answer 1

Hi Steve I will try my best to answer each of these 
My high level questions are;
1) Should I migrate everyone off Exchange 2003 onto Exchange 2010, decommission the 2003 server, and then install the second 2010 server? OR
2) Should I install the second Exchange 2010 server, migrate everyone from the first Exchange 2010 server, decommission that one, then do the migration from 2003 to 2010?
OR does it matter which way I do it?
doesn't matter at all. Since you want to move to a new hardware you can setup a new Server CASH/HUB/Mailbox. Once installed start migrating the mailboxes from Exchange 2003 to this mailbox server. This way you will not have to redo the migration from 2010
to new 2010 sever -- like you mentioned in 1) it will save you a lot of time and repeating procedure. 
I've read what I can find about installing the second Exchange 2010 server into the organisation. It seems to be pretty simple at first. Just install Exchange 2010 with HT, mailbox and CAS roles which will automatically configure it into the same Exchange organisation.
1) Do I configure CAS to be externally facing right from the get go or do I do that later?
Keep your existing 2010 internet facing for now. Once you finished migrating the mailboxes then you will need to do it.
2) As soon as I install the second Exchange 2010 server, will I encounter any mail flow problems? Will mail be trying to flow out of the second Exchange 2010 server as well as the first?
Mail will not flow to 2ndry server unless you add that server as a source serve in the transport.
In regards to SSL, so obviously the second Exchange 2010 server will have a different local domain name than the first, but ultimately, I want it to have the same external domain name, eg mail.domain.com.au. As my certificate doesn't contain any local domain
names, can I export the certificate from exch1 and import it into exch2, or should I just generate a new CSR from exch2 and get GoDaddy to reissue it?
You  can always export the certificate and then import it to the newly installed Exchange 2010.
OR should I look at creating a CAS Array from exch1 and adding exch2 to it. (I don't fully understand the workings of this at the moment).
You will only need to setup the CAS array if you are going to use both the server which can be done later.
Hope that help
Where Technology Meets Talent