Exchange 2010 with Outlook 2003 issues

Here are a couple of interesting things to be aware of when implementing Exchange 2010 with Outlook 2003 clients. Note that the issues described here do not occur with Outlook 2007 or 2010.

Service Pack:

Make sure Outlook 2003 has Office 2003 Service Pack 3 applied. If you don’t it will not work.

Enable Encyption:

Encryption must be enabled in the Outlook profile.

Under the Outlook Profile, choose “more settings” and then choose the Security tab. Make sure “Enable encryption between Outlook and the Exchange Server” is ticked.

Outlook 2003 in Online Mode

An issue exists where Outlook 2003 clients are slow when configured in Online mode. Users will notice things like moving items between folders and deleting items are slow (the item doesn’t move immediately). Cached mode resolves this issue or alternatively you can follow these steps. Note that this fix does not completely resolve the issue, but it does improve performance of Outlook 2003 online mode a lot.

On the server with the Client Access Role

  • Install Exchange 2010 Update Rollup 1 and restart the server.
  • Now make the following registry change.
  • HKLM\CurrentControlSet\Services\MSExchangeRPC\ParametersSystem
  • Create a DWORD called  “Maximum Polling Frequency”  (without quotes)
  • Make the value 10000

Note that this change is dynamic and clients will need to close and open Outlook again for the change to take affect.

Another things you can do to reduce the user impact include:

  • turning off the preview pane.
  • advising users to open the message and delete the open message, rather than deleting from the Inbox.

Send/Receive errors

I haven’t found a full solution to this problem, but it appears that users with cached mode on Outlook 2003 can get corruption in OST file or Outlook profile. To resolve this issue I have tried to deleting to OST file and creating a new Outlook profile. This works about 75% of the time.

An interesting side-effect of this issue is the Offline Address Book doesn’t download updates. I’ll post more details once I have the answer!

Microsoft Support Article

If you find this post useful, please support my attempt to win the Kordia IT Superhero Award – > Send me to NASA 

33 thoughts on “Exchange 2010 with Outlook 2003 issues

  1. We’re running into these issues as well, which is very annoying after a very smooth migration. Any progress or new tips to share?

  2. Unfortunately I haven’t made any further progress. The best you can do with Outlook 2003 is run in cached mode and service pack 3.

    I’ve found recreating the Outlook profile and rebuilding OST files on clients resolves some client side issues.

    I have another issue with public folder migration from 2003 to 2010 which I am trying to work out. I’ll posted details once I’ve figured it out…

  3. Public folder issues have been resolved. The issue was Exchange 2010 could not see the Exchange 2003 server when setting up folder replication. Installing Exchange 2010 Rollup 3 resolved this issue. It also appears to resolve the issue I had with the Offline Address Book not updating on Outlook 2003 in cached mode.

  4. Thanks for your Reply! i have troubles with opening shared calendar in outlook 2003. If i open one calendar, everything working fine. Opening a second calendar end with the following error message: outlook must be i online mode.

    Do you had the same issue?


    from Switzerland

    1. Hi Sanche,

      I haven’t seen this issue because I haven’t tried opening more than one shared calendar. I’ll try this out today and see if I get the same error.

      I am in New Zealand

  5. OAB would not replicate for me either in 2010. I had to create new OAB and rehome mailbox store to new OAB. Old OAB deleted. I restarted the MSEXCH File Distribution & Address Book Services; remounted mailbox store and view OAB in Public Folder Management Console. OAB finally replicated. Outlook 2003SP3 could not download OAB initially, but eventually downloaded. I think I had to restart Outlook.

    Hope this helps.

  6. had the same problem and found that the outlook 2003 users used ANSI OST files (probably got created while the information store in exchange 2003 didnt have an offline addressbook associated with it). Exchange 2010 only supports ANSI .ost files, if you have sp2 or (higher for outlook 2003) installed.
    if you have unicode, you are fine, else install sp2/sp3 OR re-create the ost file in unicde mode, before you migrate, else it creates a new ost file and re-syncs the entire mailbox.. – not ideal in a centrallized environment.

  7. We have the same problem with opening multiple shared calendars at the same time. Does anybody know a solution by now ?

  8. I found this post on the Internet & the Author’s name was – Andy. This successfully resolved my issues with opening shared calendars. We have recently moved to Exchange 2010 & still use Outlook 2003 for mail. The solution & I quote: “This is caused by Outlook 2003 not encrypting traffic bewtween Exchange server and client and Exchange 2010 only accepting encrypted traffic by default. Running the cmdlet Set-RpcClientAccess -Server -EncryptionRequired $False on your CAS server will resolve the issue”

  9. Hi,

    About shared calendars that do not open (except the first one) after an Exchange 200x to 2010 transition, it looks like the “path” to shared calendars are stored into the mailbox at the time your connect the calendar for the first time.
    If the shared calendar was stored on an Exchange 200x mailbox server at the time you connect to it for the first time, then the “path” to this calendar stored in your mailbox refer to an old Exchange server that is probably no more existing in yoru organization. That is why the calendar opening fails.

    What you have to do is simple :
    1) Note the shared calendar list.
    2) Remove each shared calendar.
    3) Close Outlook and restart it.
    4) Reconnect the shared calendars your noted at step 1. Now the “path” to the shared calendars should be good. It worked for me.

    What I can’t explain for now is why, when your use “Exchange Cache Mode” on Outlook 2003, you are able to open one or more shared calendar if you check them rapidly…
    If you don’t use “Exchange cache mode” you receive an error message as soon as you check a sahred calendar with an obsolete path. This behavior is expected in this case.

    I’m still searching for explanation of the cache mode behavior and I’m really interested in any hint about that.

    Have a good day.

  10. Just wanted to give you an update on the UDP issue. During the writing of, I did a new discovery. Although KB article: stated 10 seconds as the lower limite, the lower limit is actually 5 seconds polling intervals when the “Maximum Polling Frequency” key is set to “5000”.

    This has been confirmed with relevant Exchange and Outlook PMs.

    The KB article has also been updated to reflect this.


  11. I wondered if the issue with Public folders or shared Cals might also to do with settings on the Max Number of unidentied mapi connections setting – Throttling its called.

    We have an issue with Outlook 2003 SP3 clients on our new SP1 2010 server and turning on cached mode fixed many – but we have the issue of delegated users not being able to file their bosses mailboxes – turned out to be a throttling issue.

  12. I plan on upgrading our Exchange 2003 env to Exchange 2010 this coming weekend. My question to you gurus is, we still have lots of clients running Outlook XP (2002). My plan is to leave the mailboxes of the users who are still on Outlook XP on the Exchange 2003 server until they get a chance to upgrade to Outlook 2007/2010. I’m hoping by doing that I’ll avoid all these Outlook issues. does that sound like something that would work?

    Thanks in advance!

  13. Hi Charles,

    I have had the same scenario and leaving the mailboxes for Outlook XP users on Exchange 2003 until those clients are upgraded is the only choice.


  14. I had several goofy issues after installing Exchange 2010, and one of the worst was e-mails that would get stuck in the Outbox for users configured with both POP3 and Exchange accounts (even if the POP3 account was set as default). It seemed to occur mainly with Internet-bound e-mails with attachments, or addressed to multiple recipients, which would fail with:

    Sending’ reported error (0x800CCC13) : ‘Cannot connect to the network. Verify your network connection or modem.’

    This did not affect users configured for Cached Exchange Mode (a workaround). Exchange Update Rollup 4 seemed to improve, but not completely eliminate the issue. Exchange 2010 SP1 appears to have completely resolved it, and I’ve had no further complaints from users.

  15. Hi all, we had the same problem with shared calenders that did not opend after the client was migrated from exchange2003 to 2010. Every time the user opend the shared calender he get the error “The action could not be completed. The connection to the Microsoft Exchange Server is unavailable. Outlook must be online or connected to complete this action.” Our solution: If cachemode is enabled disable this mode. Close the outlook 2003 client. Start the outlook 2003 client with the parameter /cleanviews (outlook.exe /cleanviews. Enable the cache mode. thats it.
    Regards Rico

  16. I have been through the mill upgrading from Exchange 2003 to Exchange 2010.
    It would appear that I have hit every stumbling block and snag along the way.

    After many hours trawling through problem after problem for the clients to whinge that Outlook was running too slow, I just about maintained my composure !

    Steve’s posting was a real boost !!
    The slowness is greatly improved, albeit with an Offline Address Book issue.

    Looking further into the issue, it would appear that MS have released Exchange 2010 SP1 Rollup 3 which claims to have resolved the issue.

    A word of warning, when installing this Rollup, it took my server about 10 minutes to run through the pre-requisite checking. Tempting as it may be – don’t kill of the install – be patient -let it run !
    It also runs through a process called ‘Creating native images for Exchange assemblies’, which is quite protracted.
    Start to finish, my server took 22 minutes to install Rollup 3.

    After you install this update, you have to create the following registry subkey to enable the UDP notifications support feature:

    Subkey location: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeRPC\ParametersSystem
    Subkey name: EnablePushNotifications
    Type: REG_DWORD
    Value: 1

    I rebooted my server, just for the sake of completeness. But I am not sure if this was strictly necessary, I would guess that at the least you should stop and restart the Exchange Services to allow the registry change to take effect.

    Initial tests proved positive with Cached Mode disabled in Outlook 2003.
    Just have to wait for the dreaded users to start logging in now !!!

  17. Hi Jim,

    Glad you found my blog post helpful and thank you for sharing the improvements in Rollup 3


  18. Hi All,

    I’m running 2010 SP1 UR4. I’ve made the UDP Push registry change and disabled encryption, but are there any other known 2003 issues I need to be aware of before I begin moving mailboxes and removing my 2003 PF replica? Trying to insure I have all the ‘fixes’ in place before the problems are encountered. Thanks!


  19. Hi Jim,

    I think you have everything covered. I recommend migrating a couple of test mailboxes first and testing deleting in Outlook with the preview pane enabled.

    Citrix / Remote Desktop doesn’t support Outlook in Cached mode, so it is worth doing a test in Online mode.


  20. has anyone stumbled on a case where outlook 2003 clients working with RPC Proxy (RPC over HTTPS) get random “trying to connect…” status in outlook 2003 client?

    the clients are connected from different sites and when it happens it doesn’t effect all clients in that site

  21. Have you run into any issues with attachment size limits in this scenario? I have the limits turned off in exchange, but I still get an error in outlook 2003.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s