Outlook 2003 unable to connect to Exchange 2010 server

Symptoms

You are running Exchange 2010 with no service pack, or you have recently upgraded to 2010 sp1. Your Outlook 2003 client is unable to connect to your Exchange server giving one of the below error messages:-

  • 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.
  • The name could not be resolved. The connection to the Microsoft Exchange Server is unavailable. Outlook must be online or connected to complete this action.
  • 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.
  • The name could not be resolved. The action could not be completed.
  • Your Server or Mailbox names could not be resolved.

Explanation

By default Exchange 2010 (no sp) requires that Outlook clients use encryption to connect to the server. If you have recently installed Exchange 2010 sp1 this setting is retained. Outlook 2003 by default does not use encryption.

Fix 1

You can disable the requirement for encryption on the Exchange server. From the Exchange Shell run the below command:-

Set-RpcClientAccess –Server Exchange_server_name –EncryptionRequired $False

Microsoft do not recommend this for security reasons.

Fix 2

Alternatively you can enable encryption on the outlook clients. Go to the control panel, mail, account settings and tick as shown below.

Fix 3

To enable encryption on a number of computers you could use a custom group policy which you can download from here

Comments 3

  • for some reason it doesnt help,
    my client running outlook 2003 on a windows server 2008 with terminal services and i have exchange 2010 sp1 with RU4/5/6 applied, in /hosting mode.

    the encryption is disabled by default in the Exchange server. i have tried to enable/disable it on the client but i still get the same error when trying to connect.

    I scanned all the events on the client machine and didnt find any error, on the exchange server i do see successful logins in the security events, from the client machine.

    Also on the exchange server logs i see different logs from outlook 2011 clients which work fine and the 2003.

    outlook 2003 log entry:
    2011-11-03T07:40:03.046Z,11,0,/o=Interhost/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=***,hosted.*****.co.il/Microsoft Exchange Hosted Organizations/********,81.218.***.***,WIN-H2HA1HCGLQM,ncacn_ip_tcp,GetNewDSA,,6,Self,,Ntlm,

    outlook 2011 log entry:
    2011-11-03T07:49:16.577Z,1,0,/o=Interhost/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=Hagar EK Design,*******.co.il/Microsoft Exchange Hosted Organizations/******,87.69.245.146,WIN-H2HA1HCGLQM,ncacn_ip_tcp,GetFQDNFromLegacyDN,,79,,,Ntlm,

  • thanks, no, didnt see such option in outlook 2003…

    it fails on “check names” process in Mail(32), so i guess its not related to cached mode or so… not sure…

    i’ll search for it and will try anyway and keep you updated

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