Common Client Access Considerations for Outlook 2003 and Exchange 2010

There are several scenarios for consideration when deploying Exchange Server 2010 in an environment where Outlook 2003 is used. Most of these scenarios have been documented prior to the product release and some applied to previous versions. However, in a review of support cases, we’ve found that they have not been used prior to contacting Microsoft.

This post introduces some of the scenarios and the articles that will resolve these issues. If you’re planning a deployment of Exchange 2010, understanding client configuration and the requirements and capabilities of your organization are of importance to the user experience. Primarily field office environments or environments where users are not joined to the domain, profile distribution, or the ability or inability to enforce policies or distribute the solutions will dictate how you address the issue.


This is a top support issue for Outlook 2003 access to Exchange 2010.

Note: In Exchange 2010 Service Pack 1, the RPC encryption requirement has been disabled by default. Any new Client Access Servers (CAS) deployed in the organization will not require RPC encryption. However, any CAS servers deployed prior to SP1, or upgraded to Service Pack 1, will retain the existing RPC encryption requirement setting. Also bear in mind disabling the RPC encryption requirement on a CAS server won’t lower the security between Outlook 2010/2007 and any CAS server as RPC communication for these Outlook versions will remain encrypted.

Exchange 2010 introduces additional “out of the box” security for client communications with the Exchange Server — encryption between the client and the server is enabled, by Default. This is RC4 encryption – where the client negotiates the encryption level based on the client operating system’s capabilities, up to 128-bit encryption. This is documented in the following topic in Understanding RPC Client Access

Prior to Outlook 2007, encryption was not enabled on the client side, by default. However, if profiles for Outlook 2007 exist where encryption is disabled, or if Outlook 2003 profiles created with default settings are used with Exchange 2010, the connection will fail when Outlook attempts to connect to an Exchange Server 2010 mailbox. One or more of the following common error messages will be displayed:

  • Cannot start Microsoft Office Outlook. Unable to open the Outlook window. The set of folders could not be opened.
  • Unable to open your default e-mail folders. The Microsoft Exchange Server computer is not available. Either there are network problems or the Microsoft Exchange Server computer is down for maintenance.
  • The connection to the Microsoft Exchange Server is unavailable. Outlook must be online or connected to complete this action.
  • Unable to open your default e-mail folders. The information store could not be opened.
  • Outlook could not log on. Check to make sure you are connected to the network and are using the proper server and mailbox name. The connection to the Microsoft Exchange Server is unavailable. Outlook must be online or connected to complete this action.

There are several methods to work around this issue, from immediate manual change by the administrator or the user, to deployment of administrative templates or new profiles. Each of these scenarios is documented in the Microsoft Knowledge Base article 2006508: Outlook connection issues with Exchange 2010 mailboxes because of the RPC encryption requirement

New Mail Notifications and UDP

Exchange 2010 no longer supports UDP for new mail notifications. However, Outlook 2003 relied primarily upon UDP notifications to display new messages and changes to folders. The result is that Outlook 2003 users will see delays in updates to folders and the Send/Receive process appears to take a long time. For more details about the issue and two possible resolutions for the organization, see In Outlook 2003, e-mail messages take a long time to send and receive when you use an Exchange 2010 mailbox

Update 1/28/2010: UDP notification support has been added to Exchange 2010, and will be available in Exchange 2010 SP1 Update Rollup 3, slated for March 2011. For details, see UDP Notification Support Re-added to Exchange 2010.

Address Book Service (Directory Access)

Directory access has changed in the Exchange Server 2010 world. The TechNet topic Understanding the Address Book Service introduces the changes and is currently being updated with more information.

A future topic will cover this in more detail.

Public Folders, Offline Address Book and Free/Busy

Outlook 2003 uses the Public Folders free/busy messages to determine availability in the Calendar and as the source for Offline Address Book (OAB) synchronization. If Public Folders are not configured during Exchange 2010 setup, OAB and Free/Busy will not be available to Outlook 2003 users. These users will encounter connection errors.

If free/busy Public Folders folder is not replicated to Exchange 2010, users will encounter the issue mentioned in Users who use Outlook 2003 cannot publish their free/busy data in Exchange Server 2010 or in Exchange Server 2007

If clients inside the organization or connected via VPN/RAS, and the organization uses a Proxy server, the Client Access Server should be listed in the “Bypass proxy server for local addresses” configuration.

Error message when Outlook synchronizes an offline address book with Exchange Server 2007 and Exchange Server 2010: “0x8004010F”

Also, if there are missing address book list objects or missing or incorrect address lists, the following may occur:

An error occurs when you try to synchronize the offline address list on an Exchange Server server while you are using Outlook 2003: “0x8004010F”

Opening Additional Mailboxes

Delegate Access issues, opening other user’s folders or mailboxes are a common operation in the enterprise. Outlook 2003 users may encounter issues, if the environment is not properly prepared for their use:

Office Outlook 2003 does not connect to two or more additional mailboxes in a mixed Exchange Server 2007 and Exchange Server 2010 environment

An error occurs when an Exchange server 2003 user tries to open more than one delegate mailboxes of Exchange Server 2010 in Outlook 2003

RPC over HTTP Connectivity

The following article discusses issues with Outlook 2003 connectivity when the RPC proxy server extensions do not load correctly. This article also applies to Exchange Server 2010 connections.

Error message when Outlook 2003 users connect to an Exchange server by using RPC over HTTP: “Server Unavailable”

Unified Communications

Integration features with Office Communicator and functionality with Office Communications Server have been documented in the following documents:

The presence information for a Communications Server user may not appear, or may appear intermittently, in Outlook 2003 Service Pack 2 or in Outlook 2007

*Communicator does not update the free/busy information as scheduled

*Note: This functionality is not available to Outlook 2003/Exchange Server 2003 users, as the Availability Service functionality is required for both the client and the Exchange Server. The only method to obtain this functionality is to upgrade both the client and the server(s).

Update 10/12/2010: Added a note about RPC Encryption setting on Exchange 2010 SP1 servers.

Will Duff

Comments (14)
  1. alex says:

    So given all this, if my organization is running Exchange/Office 2003, and we wish to upgrade to Exchange/Office 2010, would Microsoft recommend that we deploy Office 2010 before upgrading Exchange? Or will this give us an equally lengthy list of ‘gotchas’?

  2. LilWashu says:

    Despite the easily-resolved RPC encryption problem being the "top support issue", the lack of UDP notifications is a real killer if you can’t use cached mode to overcome it. Unless you are happy for your users to have to wait random amounts of time between 5 and 10 seconds for any changes in their mailbox to become apparent, and deal with error messages if they attempt to force the issue, Outlook 2003 in online mode with Exchange 2010 is a complete non starter and should never have been considered "compatible".

    Extra icing on the cake is not being able to roll back to Exchange 2007 if you have installed Exchange 2010 in your environment.

  3. Ricardo Duarte says:

    May I add that attachments will also no show on Outlook 2003 when the message is digitally signed. You either have to flag the message, open it and "save all attachments" or forward the message.

    Really annoying.

  4. Pugu says:

    While this article is a good place to start to find links to all the technet and KB articles, it would have been better if you have given a step by step guide to making outlook 2003 work in a 2010 environment.  Particularly, the address book link tells us nothing.  It’s nice to have a background as to why you need to make a change to get something to work, but it’s a very microsofty thing to paste a technical article to make the reader figgure out what change they need to make in the first place.

  5. marcelmartines says:

    "While this article is a good place to start to find links to all the technet and KB articles, it would have been better if you have given a step by step guide to making outlook 2003 work in a 2010 environment.  Particularly, the address book link tells us nothing.  It’s nice to have a background as to why you need to make a change to get something to work, but it’s a very microsofty thing to paste a technical article to make the reader figgure out what change they need to make in the first place."

    You are so right :-)

  6. Mike Crowley says:

    Agree with Pugu.  The address book article does not talk about address books.

  7. raf says:

    We upgraded our systems to Exchange 2010 couple of weeks ago. To be perfectly honest the only problem we had was a non-domain joined PC with Office 2003 installed, the rest went smooth. I would recommend to apply the latest SP for Office 2003 and all updates (it should be done any way).

    Great article Will btw!

  8. Conrad says:

    Frankly, If I am requested, I’ll tell our customer "Exchange 2010 Require at least outlook 2007"…

    We had to discover all these problem and unsatisfying workarounds to late….

    Best advice, upgrade the client before! Outlook 2003 isn’t 7 year older than the server part?…


  9. Norah says:

    What will be the behavior at Outlook 2003 during *over?

  10. John Strachan says:

    How about putting it somewhere obvious in the Exchange 2010 technet documentation – under system requirements, for example (or at least in the "planning" section? At the moment, it’s hidden away in "Understanding Client RPC Access" –

    I’m sure lots of people have been upgrading to Exchange 2010 now, followed by an upgrade from Office 2003 to 2010 later in the year. They are then hit by hit by the loss of UDP notifications and their user say "Exchange 2010 is much slower than the old version"!

  11. Will Duff - MSFT says:

    All, thanks for the additional comments and suggestions.

    Your points are well taken.  I’m working with my counterparts in the org to product a TechNet topic for the Exchange 2010 tree.  This post is the "first step".

  12. Al Macmillan says:

    Agree with LilWashu, the lack of UDP and the only ‘real’ way round it to use cached mode to overcome it makes using Outlook 2003 a joke. I really wish I’d known this before I upgraded. Even using KB2009942 to reduce the polling value still makes it unusable!

  13. PaulM says:

    If Microsoft really cared about their customers they would not have released Exchange 2010 without UDP support without making it VERY CLEAR that Outlook 2003 is NOT COMPATIBLE.  Our users are extremely unhappy post migration and the solutions put forward by Microsoft are not solutions at all particularly since our organisation runs Terminal Services which cannot utilise cache mode.

    Its easy for Microsoft to say upgrade to Office/Outlook 2007 or 2010 – but we have not budgeted for such an upgrade budgeted for this FY.

    All we wanted was a new Exchange Server and our users to notice no difference in their usage of the system – the result has been far from this.  Had Microsoft made it clear that Outlook 2003 was NOT COMPATIBLE with Exchange 2010 we would have upgraded to Exchange 2007. Now we’re in a trap not of our own making.

    Anyone else like to share their experience with Microsoft being less than forthcoming on this critical issue?

  14. A. Gotink says:

    The lack of UDP notifications is a real pain-in-the-as for Outlook 2003 users. I tried the Exchange 2010 SP1 beta. It seems to me that the Outlook 2003 problem is solved!! Great !!

    I tried it whith 1 CA server with and 1 CA server without sp1.

    Is UDP back?

    Can someone confirm this?

Comments are closed.