So another set of common questions I get is “Do I need to run Outlook 2010 after I migrate to Exchange 2010?” or “What don’t I get if I’m still on Outlook 2007 in an Exchange 2010 environment” or “Can I still use Outlook 2003 against Exchange 2010?” or “Which Outlook 2010 features work against an old Exchange 2003/2007 Environment?” Here are answers to these and many other similar questions…
Do I need to run Outlook 2010 after I migrate to Exchange 2010? / Can I still use Outlook 2003 against Exchange 2010?
Simple answer, NO, you do not need Outlook 2010 to use Exchange 2010 and in fact if you transition from Exchange 2003 or Exchange 2007 to Exchange 2010, if you use the migration tool to move your mailboxes to Exchange 2010, your Outlook 2003 or Outlook 2007 users won’t even know you moved them to Exchange 2010. Exchange 2010 still supports MAPI access and Outlook Anywhere (RPC/HTTPS) to Exchange, so when a user’s mailbox is moved to Exchange 2010, the user still keeps their old Outlook 2003 / 2007 client.
Note: the trick during the migration process is after you “move” a user’s mailbox from Exchange 2003 or Exchange 2007 to Exchange 2010, keep the old 2003/2007 server running for a couple weeks. The next time the user launches Outlook, their Outlook profile is still configured to point to the “old” Exchange 2003/2007 server. But if you keep the old server online, when Outlook tries to connect to the old server, the old server will tell Outlook that the user’s mailbox has been moved and it’ll tell Outlook to automatically update the Profile to now point to the new location of the user’s mailbox (ie: the new Exchange 2010 server). After a couple weeks you’ll find most (90%+) of your users will have launched and run Outlook and their profiles will have automatilly changed meaning NO admin intervention to update the users profiles. You can now uninstall the old Exchange 2003/2007 server, however you’ll have a handful of users whose profiles will not have switched over if the users were out on extended leave and hadn’t connected to Outlook in the couple week period you had the old Exchange server running (for these users, you just go into their Outlook profile and point them to the new Exchange 2010 server)
Back to Outlook 2010 though, so you can most certainly use older version of Outlook against Exchange 2010. The users will get all of the features that the version of Outlook (2003/2007) they are running. Microsoft does not officially support Outlook prior to 2003 against Exchange 2010, so Outlook XP, Outlook 2000, etc are “not supported”.
What don’t I get if I’m still on Outlook 2007 in an Exchange 2010 Environment?
There are a number of features that are specific to Exchange 2010 that “require” the 2010 client. And I was very careful to say “2010 client” as these are features in Outlook 2010, but they are also features that work in Outlook WebApp (OWA) 2010. So, for now (Nov/2009) you can download and use Outlook 2010 Beta against Exchange 2010 and get these features, OR you can just use the out of the box OWA 2010 Web access to Exchange 2010 for these features.

These features include:
This is just a sample list of features in Exchange 2010 that require a 2010 client (Outlook or OWA) to gain access to the features. And as a note, it’s not like the features aren’t there, they just can’t be accessed by users without the 2010 client, so other users that have Outlook 2010 can access the features, or a person can switch between Outlook 2003 and Outlook 2010 and when they are on Outlook 2010 they have/see the features, when they are on Outlook 2003, the features are no exposed to that Outlook 2003 user.
Which Outlook 2010 features work against an old Exchange 2003/2007 Environment?
For users whose networks are still running Exchange 2003/2007 but want to try out Outlook 2010, what new features do you get when using an older Exchange email system?: The answer is a “LOT” of features in Outlook 2010 will work against an older Exchange 2003/2007 environment. In fact, you can almost take the list above on the new Exchange 2010 features as most of those features (archive mailboxes, Exchange control panel, Protected voicemail” are Exchange 2010 features that obviously won’t be in earlier versions of Exchange. But some of the features you’ll get by going to Outlook 2010 in an Exchange 2003/2007 environment:
Overall, users who have already begun using the Office 2007 will find the Outlook 2010 client to be very familiar with the Ribbon feature at the top. For those who are switching from Office 2003 to Office 2010 for the first time will find the new Ribbon a little new and unique, however most people in email simply create new emails and appointments, read emails, and save/print emails. All the basic features for email can be picked up in just a minute or two and in fact our experience has shown for first time email users, the new Outlook 2010 interface is very intuitive and easy to use.
Microsoft has made Outlook 2010 available for download, those who want to fiddle with it can load it up in an existing Exchange 2003 / 2007 environment and using Outlook 2010 today, or use Outlook 2010 against an Exchange 2010 server and get even more features and enhanancements. Bottomline, Outlook 2010 and Exchange 2010 are not dependent on each other. You can upgrade to Exchange 2010 to get all of the features in Exchange 2010 such as Database Availability Groups (for high availability and disaster recovery), use E2010 to Outlook WebApp premium client access for non-Windows clients like Apple Mac and Linux, use E2010 for better scalability and reliability. ADD Outlook 2010 down the line to add/enhance the capabilities supported in Outlook 2010 or use OWA 2010 to get the features right after going to Exchange 2010.
Rand Morimoto has been in the computer industry for more than 30 years and has authored, co-authored, or been a contributing writer for a couple dozen books on Microsoft Windows, Security, Exchange email, BizTalk Server, and remote and mobile computing. Rand is the president of Convergent Computing, an IT consulting firm that has been one of the key early adopter program partners with Microsoft, implementing beta versions of Microsoft technologies 2-3 years before the product releases to the public. This provides Rand and the consultants in his company extensive knowledge on the technologies long before the products are generally available.
Besides speaking at more than 50 conferences and conventions around the world in the past year on tips, tricks, and best practices on planning, migrating, and implementing technologies, Rand is also head judge for the worldwide Imagine Cup competition, is a Board member for the Chabot Space and Science Center and planetarium, and a Regent for the Board of Saint Mary's College of California.
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