Exchange 2010 SP1 OWA internal & external names

I'm in the process of planning my slow migration from Exchange 2003 to 2010 SP1 and want to keep thing as simple as possible for users. I have ready article that state you need to have both an internal and external name for our OWA site . Is it ok if I just use an external name only? I don't want confuse my user's?
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Auric1983Connect With a Mentor Commented:

There are a couple powershell commands you need to execute to set the internal name to the external owa address, but you are 100% correct.

It's just na extra layer of confusion from MS is all :D
You need external name and separate external IP so both versions of Outlook Web Access will work.

We are talking about the Exchange2003LegacyURL here aren't we?
You won't confuse your users cause as far as they are concerned they hit and if they are Exchange 2003 users then Exchange 2010 will log them into e2k3 OWA via and then pass the URL back to the user.
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Using a split DNS you can set it up so your internal DNS name and external DNS name for OWA are the same...
compdigit44Author Commented:
Ok, let me make sure I'm understanding thing correctly..

1)As I slowly migrate to Exchagen 2010 will both my 2003 and 2010 users be able to access there OWA's via the CAS server? What are the steps for setting this up

2) I have ready articles that state you should have and internal owa name and external owa name for 2010. For example internal = server.domain.local external = can I just have an external owa name to make things simple

3) On the certifcate requete what is the purpose of the Legacy server box? do I need to type in the full internal FQDN name of my 2003 server here?

1. You will need to move your legacy server to "" your new server will be or whatever name.

2. There are a number of services that have internal and external URL's, OWA being one of them.  That being said, using split DNS and a few configuration commands you can set it up so the URL's are the same so the user only  needs to know "" and not the server name.  

3. The legacy server on the cert is to do with the legacy server above (see #1)  Depending on how fast you do the migration you may not need this.

This is the guide I used when i migrated my site to 2010 this year...

compdigit44Author Commented:
I will review the link you sent - thanks

1) I'm unclear by what you mean by moving to

2) under 2003 you had one OWA site in our case it is in the DMZ. Why under 2010 do you need both a internal and external owa name
1. In order for your legacy clients to have OWA access you need to specify the legacy server name in this case, basically any instance of will get changed to  You then update your '' to point to your new server (needs another external IP)

2. In 2010, it is not supported to have the CAS role in the DMZ. see for more information.   The only roles that can be deployed in the DMZ are the Edge servers which require additional configuration & setup.  (They cannot be domain members etc.)

The way I did my migrations here

1. Setup & Configure new exchange server
2. Configure routing connector between the two (Ex 2003 was still doing mail delivery)
3. Moved users to Exchange 2010
4. Changed NAT rule on firewall so the external records for etc. all pointed to my new server
5. Removed Exchange 2003

How many users are you migrating?
compdigit44Author Commented:
The link you provide was very helpfuly. I still having a hard time understanding WHY in 2010 I need both and internal and external OWA URL

for example internal : https://server.domain.local  external

What ould happen if you left the internal OWA URL blank?

on the certificate request for the legacy host name: do I put in the internal domain name of my Exchange 2003 server ex2k3.domain.local???

Long & short of it is, by default internal clients will refer to the server by it's internal name (unless told otherwise) The reason I say that is there are times when your internal FQDN cannot be added to a certificate.  For example if your internal FQDN was and you didn't actually Own the domain on the web a cert authority would not give you a cert for that, so split DNS is used.

In my environment, the split dns is setup so that "" resolves to the external address outside and the internal ip address inside, so I only need to tell my users one URL.

If you are using a SAN certificate you can just include both the and the ex2k3.domain.local request, but it's probably not required.

compdigit44Author Commented:
Ok I think I'm being to understand but in regards to OWA access I can just tell my users to new external OWA 2010 address and setup the proper internal DNS so they can access this site from the inside, I should be all set correct?
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