here was a problem connecting to Microsoft Office Outlook. The email address used in your default Outlook profile is different from the sign-in address used in Lync 2010. Change your default Outlook profile to match the sign-in address you are using in Lync, and then sign out and sign back in to Lync.

Scenario 1: The email address that is used in your default Outlook profile differs from the sign-in address that is used in Lync 2010

Verify the user's primary SMTP address. Make sure that the Outlook profile that is created uses an email address that matches the Session Initiation Protocol (SIP) address. To do this, follow these steps:

1. Open Control Panel, and then click Mail.
2. Click E-mail Accounts. The email address that is listed should match the SIP address.
3. If the listed email address does not match the SIP address, re-create the Outlook profile. When you re-create the Outlook profile, manually enter a matching SIP address.

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Scenario 2: Outlook is not installed or configured correctly

Repair or reinstall Outlook, and then sign out and sign back in to Lync. To do this, follow these steps:

1. Uninstall Lync 2010, and then repair the Microsoft Office installation.
2. If repairing Office does not resolve the issue, perform a fresh installation of Lync 2010 and Office in the following order:
   1. Uninstall Office.
   2. Uninstall Lync 2010.
   3. Reinstall Office.
   4. Set up and configure an Outlook profile.
   5. Reinstall Lync 2010.

If the earlier steps do not resolve the issue, edit the registry. To do this, follow these steps:

1. Click Start, click Run, type regedit, and then press Enter.
2. Locate and then delete the following registry subkey:
   
   HKEY_CURRENT_USER\Software\Clients\Mail
   
3. Locate the following subkey, and then make sure that Outlook is set as the default mail client:
   
   HKEY_LOCAL_MACHINE\Software\Clients\Mail
   
4. Restart the computer.

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Scenario 3: You receive the "Lync is in the process of determining the location of Exchange Web Services" or the "Lync cannot connect to the Exchange server. Lync will attempt to retry the connection" error message

These messages typically occur when you install Lync 2010, and they should disappear after several minutes. If one of these error messages persists or changes to another Outlook integration error, follow the steps in the scenario that is most appropriate for the error.

One of these errors may also occur when you enter incorrect credentials when you are prompted to connect to your Outlook profile or if you opt to click Cancel. To resolve the issue, sign out and then sign back in to Lync, and then enter your credentials. If your credentials are not accepted and you are continuously prompted for credentials, see the following article in the Microsoft Knowledge Base:  

2298541  Microsoft Lync 2010 continuously asks for credentials after signing in

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Scenario 4: You cannot connect to Exchange Web Services (EWS) to retrieve Calendar and Out of Office information

Lync relies on EWS to retrieve information for Availability, for Free/Busy, for Out of Office, and for Contact Search. If the AutoDiscover service is not set up correctly, see the following Microsoft TechNet article:

DNS Troubleshooting for Exchange Online

You can follow these steps to verify that AutoDiscover for the user’s Exchange mailbox is working correctly:

1. Verify that Exchange Free/Busy is working in Outlook. To do this, follow these steps:
   1. Start Outlook, and then create a new meeting invitation.
   2. Add several contacts to the invitee list. Then, click Scheduling Assistant and verify that you can see when people are available or busy.
2. If the Free/Busy information for users is displayed as hashes (/////), it is likely that there is something wrong with the Exchange Free/Busy service. Verify the AutoDiscover service. To do this, follow these steps:
   1. Press and hold CTRL, right-click the Outlook icon in the notification area, and then click Test E-Mail AutoConfiguration.
   2. Enter the user’s SIP address and password. This verifies that Lync can determine your EWS endpoint based on your SIP address.
3. Clean Outlook Free/Busy information. To do this, follow these steps:
   1. Open a command prompt. To do this, click Start, click Run, type cmd, and then press Enter.
   2. Move to the Outlook installation folder:
      • Office 2010: C:\Program Files\Microsoft Office\Office14
      • Office 2007: C:\Program Files\Microsoft Office\Office12
   3. Type "outlook.exe /cleanfreebusy", and then press Enter.
4. Verify the Lync EWS external URL. To do this, follow these steps:
   
   1. Press and hold CTRL, right-click the Lync icon in the notification area, and then click Configuration Information.
   2. Enter the EWS External URL value into a web browser. If you are prompted, enter your Office 365 credentials. You should see the Exchange Web Services XML document displayed in the web browser.
5. Add Exchange and Lync URLs to the Trusted sites list in Internet Explorer. To do this, follow these steps:
   1. Open Internet Explorer, and then click Internet Options on the Tools menu.
   2. Click the Security tab, click Trusted sites, and then click Sites.
   3. Add the following URLs to the list of trusted sites:
      • http://*.outlook.com
      • http://*.lync.com
      • http://*.sharepoint.com
      • Click Close, and then click OK.                               
      • http://support.microsoft.com/kb/2436962