I have been in the process of writing this blog for a long time and now it’s finally here. The reason for this blog is that after you install Exchange 2010 you can no longer install a previous version of Exchange into the same organization (in a supported way). You might think that that is not a problem and you are probably right but there are two scenarios when you might run into problems.

1. If you ever need to migrate from Lotus Domino to Exchange
2. If you need WebDAV

Migration

Let’s talk a bit about the first scenario and why this might be a problem.

When you perform you Schema updates for Exchange 2010 (or run the setup witch will update the schema for you) you will be prompted with a warning:

Setup is going to prepare the organization for Exchange 2010 by using ‘Setup /PrepareAD’.  No Exchange 2007 server roles have been detected in this topology.  After this operation, you will not be able to install any Exchange 2007 server roles.

So when you want to migrate mailboxes from Lotus Domino you could do that with Microsoft Transporter Suite. As stated in the overview it’s only supported for Exchange 2007

Transporter Suite contains a set of tools for migrations from both Lotus Domino Servers, and generic IMAP/POP sources. For Lotus Domino the suite contains a set of tools for Directory and Free/Busy interoperability between Lotus Domino 6, 7 and 8 and Exchange Server 2007 and Windows Server 2003/2008 Active Directory. In addition for Lotus Domino the suite contains migration tools to migrate users, groups, personal address lists, mailboxes, personal mail archives, and applications from Lotus Domino 5, 6, 7 or 8 to Active Directory, Exchange Server 2007, and Windows SharePoint Services 3.0. For generic POP/IMAP servers the suite contains a set of tools to bulk migrate mailboxes from any generic email servers that support the POP3 or IMAP4 protocol to mailboxes in Exchange Server 2007

There is no Transporter Suite for Exchange 2010 so this means that you would have to use a Exchange 2007 server to migrate your Lotus Domino data to Exchange.

So if you are about to install Exchange 2010 and might need to migrate from Domino, think about installing a Exchange 2007 first. Please also read the last part of this blog for more info about things to think about

If you already installed Exchange 2010 and now find you self in a situation where you need to migrate Domino to Exchange 2010 there are some third party tools you can use, BinaryTree and Quest.

WebDAV

The second reason for installing a Exchange 2007 server before you install Exchange 2010 could be WebDAV. WebDAV is not a part of Exchange 2010 so if you have systems that use WebDAV you will need to have a Exchange 2007 server for that purpose.

Things to think about

If you for any reason needs a Exchange 2007 server on your way to Exchange 2010 there are some things you should think about:

Routing Groups

When you install a Exchange 2007 Hub Transport server into a Exchange 2003 organization you will be asked to point out a Exchange 2003 server. The reason for this is to set up a routing group connector between Exchange 2003 and Exchange 2007.

Screenshot from Exchange 2007 setup

After you select a Exchange 2003 server setup will create a routing group connector between the server you install and the selected Exchange 2003 server. So what’s the problem with that? Well since the dialog in the screenshot above only will show up when you install your first Hub Transport server there is a possible risk of single point of failure and if you only have your Exchange 2007 server for “better safe then sorry” purpose then you might not care that much about it an possible even shut it down with the result of no mail flow between Exchange 2003 and 2007/2010.

To avoid that to happen you can use Exchange Management Shell to configure the RGC with multiple bridgehead servers.

[PS] C:\>Set-RoutingGroupConnector <Name of RGC> -TargetTransportServers <Name of Exchange Server> -SourceTransportServers <Name of Exchange Server>

Note: By default there are two routing group connectors created, enter multiple Target and Source Transport servers on both.

When you install your Exchange 2010 Hub Transport Servers it’s a good idea to include them as well.

Virtual Directories

After you install your Exchange 2010 servers you probably don’t want clients to access the “temporary” Exchange 2007 box so the are a few things to configure to avoid that.

Here are the settings I change (in these examples loadbalancer.mailmaster.local represent the internal Exchange 2010 load balancer and webmail.mailmaster.se the external URL, in my case a TMG Server)

Set-ClientAccessServer Exchange2007server -AutoDiscoverServiceInternalUri:"https://loadbalancer.mailmaster.local/Autodiscover/Autodiscover.xml"

Set-OwaVirtualDirectory "Exchange2007server\owa (Default Web Site)" -InternalUrl: “https://loadbalancer.mailmaster.local/owa” -ExternalUrl:”https://webmail.mailmaster.se/owa”

Set-ActiveSyncVirtualDirectory "Exchange2007Server\Microsoft-Server-ActiveSync (Default Web Site)" -InternalUrl: “https://loadbalancer.mailmaster.local/Microsoft-Server-ActiveSync” -ExternalUrl:”https://webmail.mailmaster.se/Microsoft-Server-ActiveSync”

Set-OabVirtualDirectory "Exchange2007Server\OAB (Default Web Site)" -InternalUrl: “https://loadbalancer.mailmaster.local/oab” -ExternalUrl:”https://webmail.mailmaster.se/oab”

Set-WebServicesVirtualDirectory "Exchange2007Server\EWS (Default Web Site)" -InternalUrl: “https://loadbalancer.mailmaster.local/EWS/Exchange.asmx” -ExternalUrl:”https://webmail.mailmaster.se/EWS/Exchange.asmx”

If you perform the above you can shut down your Exchange 2007 server and there will still be mail flow and client will still be able to connect to your Exchange 2010 servers.

Some other questions I can imagine can arise…

Q: Can I shut down the “temp Exchange 2007 server” and forget about it?

A: No! If you do the computer object will get tomb stoned in  Active Directory so the server should be online once in a while to prevent that. If you want to check how long you tombstone time is, check this out

Q: Can I uninstall the “temp Exchange 2007 server” and reinstall if needed?

A: No! To be honest I have tried that and I can actually get it to work but I have asked this question to members of the Exchange product group and got a no. It might be that it hasn’t been tested…

Q: How do I uninstall the “temp Exchange 2007 server” when I no longer need it (and I’m SURE I don’t need it)?

Nothing special here, you uninstall it like you would with any Exchange 2007 server, here’s a How to…

Q: Do you really install this “temp Exchange 2007 server” at every customer before you install Exchange 2010?

A: No! But I make sure the customer understands the pros and cons with that BEFORE I install Exchange 2010

Q: Will there be a change in SP1 regarding this?

A: To my knowledge no!

Additional information:

Cannot install Exchange 2007 roles after you prepare Active Directory for Exchange 2010

Installing Exchange 2003/2007 in an Exchange 2010 Environment