Outlook hangs when it connects to an Exchange Online mailbox that was migrated from on-premises Exchange Server

Applies to: Exchange Online

PROBLEM


Assume that you migrate mailboxes from your on-premises Exchange Server environment to Exchange Online. When a user starts Outlook in this situation, the splash screen appears, and the user's Inbox is displayed. However, if the user takes any other action in the Outlook window, the title bar changes to Not Responding and remains like this for several minutes.

CAUSE


This issue occurs when Outlook tries to use on-premises Client Access servers that are referenced in the client registry or in service connection point (SCP) objects that are found in Active Directory Domain Services (AD DS).

SOLUTION


Important
Follow the steps in this section carefully. Serious problems might occur if you modify the registry incorrectly. Before you modify it, back up the registry for restoration in case problems occur.

To resolve this issue, set the value of the ExcludeSCPLookup DWORD value in the HKEY_CURRENT_USER\Software\Microsoft\Office\<x>\Outlook\Autodiscover registry key to 1. To do this, follow these steps:
  1. Exit Outlook.
  2. Click Start, type regedit in the search box, and then press Enter to open Registry Editor.
  3. Locate and then select the following registry key:
    HKEY_CURRENT_USER\Software\Microsoft\Office\<x>\Outlook\AutoDiscover
    Note In the registry key path, <x> corresponds to the version of Outlook that's installed:
    • For Outlook 2013, <x> is 15.0
    • For Outlook 2010, <x> is 14.0
    • For Outlook 2007, <x> is 12.0
  4. Do one of the following:
    • If the ExcludeSCPLookup DWORD value already exists, go to step 5.
    • If the ExcludeSCPLookup DWORD value doesn't exist, create it. To do this, follow these steps:
      1. On the Edit menu, point to New, and then click DWORD Value.
      2. Type ExcludeSCPLookup, and then press Enter.
  5. Right-click ExcludeSCPLookup, click Modify, type 1 in the Value data box, and then click OK.
  6. Exit Registry Editor, and then restart Outlook.

MORE INFORMATION


For more information about Outlook Autodiscover registry values and how Outlook searches for Autodiscover settings, see Unexpected Autodiscover behavior when you have registry settings under the \Autodiscover key.


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