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Outlook cannot connect to Exchange 2010

I’ve been working with a customer lately who had issues with Outlook 2003 unable to connect to Exchange 2010.

These are some of the error messages Outlook may throw:

Your Exchange Server administrator has blocked the version of Outlook that you are using. Contact your administrator for assistance.

Outlook 2003 users who are connecting to Exchange may receive one of the following error messages:

 

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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.

Cannot start Microsoft Office Outlook. Unable to open the Outlook window. The set of folders could not be opened. The server is not available. Contact your administrator if this condition persists.

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Upon probing I found that the exchange admin had introduced a new server into the org and replaced the ip for the old server with the new one. That aint the best thing to do but the damage was done as Exchange was uninstalled from the old box.

They did not have a CAS array created and as a result, Outlook was pointing to the FQDN value of the old CAS Server. Any user with a pre-existing Outlook profile configured to point to a CAS name and not the CAS array object will continue to connect to the CAS name and it will not update itself to utilize the CAS array object FQDN. This behavior is by design.

My first step was to ensure the RPCClientAccessServer attribute reflects the name of the old server since they did not have a CAS array.

Get-MailboxDatabase | fl Name, RpcClientAccessServer

This should point to the CAS array object or the FQDN value of the new CAS server. In our case, the admin had clearly no idea what he was doing and it was pointing to the old server.

I used the following cmdlet to change the attribute:

Get-MailboxDatabase | Set-MailboxDatabase –RPCClientAccessServer “New CAS FQDN”

Outlook 2010 and 2007 users started connecting the moment this was implemented but no luck with Outlook 2003.

I will cut the mystery and explain what ultimately resolved the issue:

Get-ClientAccessServer | Set-RPCClientAccess –EncryptionRequired $False 

This disabled the RPC encryption requirement and confirmed Outlook 2003 was able to connect.

It was confirmed that the new server was installed as an RTM server and later upgraded to SP1. Exchange 2010 RTM has RPC encryption enabled by default and when SP1 is installed, it does not change this setting By default, the requirement for RPC encryption is turned off in Exchange Server 2010 Service Pack 1 (SP1).

It is highly recommended that a ClientAccessArray be created, even if a single Exchange server exists. This way all clients will point to the array name as opposed to the individual client access servers. If one client access server is to become unavailable and a 2nd one is available in the same AD site, Outlook clients will not be affected.

Ratish Nair
MVP Exchange
Team@ MSExchangeGuru

8 Responses to “Outlook cannot connect to Exchange 2010”

  1. Nimesh Says:

    Dear Ratish,

    its not right practice to disable RPC encryption at Exchange end, you can enable the encryption in outlook 2003

    Regards,
    Nimesh.

  2. Ratish Sekhar Says:

    Naah – cant agree… Encryption is disabled by default in Exchange 2010 SP1 and above…
    Exchange 2013 has it enabled coz it doesnt support Outlook 2003…

    Get-RpcClientAccess | ft Server, EncryptionRequired

  3. Blog Posts of the Week (2nd - 8th December 2012) - The South Asia MVP Blog - Site Home - TechNet Blogs Says:

    [...] Outlook cannot connect to Exchange 2010 [...]

  4. David Burkhart Says:

    Thanks, Ratish. I had this same issue – replaced an Exchange 2007 Hub/CAS server with an Exchange 2010 Hub/CAS with the same name and IP address (though I did deinstall Exchange 2007 from it). I had to do this due to issues we were having in our migration. Regardless, your information helped me resolve the connectivity issue I was having with my Outlook 2013 clients. Thank you!

  5. Ratish Sekhar Says:

    Glad to help… :-)

  6. ZAHOOR Says:

    i have new exchage 2010 with typical instalation wiht SP3
    i am getting the below when trying to configure outlook 2007.

    Web App is workign fine.
    the name cannot be resolved. The Connection to Microsoft Exchange is unavailable. outlook must be online or connected to complete this action

    please help

  7. Srikanth.N Says:

    It really helped me a lot thanks!!!

  8. Mustafa Says:

    Outlook 2003 randomly shows disconnected from exchange 2010 SP3. outlook 2007 and outlook 2010 clients work fine….
    Please suggest..

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