Possible Outlook mail flow issue using iCloud add-in

Applies to: Microsoft Outlook 2010Outlook 2013


When using Microsoft Outlook with certain versions of the Apple iCloud Outlook add-in installed, the following mail flow issue has been seen by Microsoft Support teams:

  • Messages may remain or appear to be stuck in the Outbox folder

NOTE: The use of the Apple iCloud Outlook add-in does not necessarily mean you will see this symptom, even if you have the version specified below under Cause. And, there are definitely other causes for messages stuck in the Outbox. This article is merely intended to help you identify possible causes of this symptom when using Outlook.


The symptom listed above has been seen with the following version of Apple iCloud file:

File: APLZOD32.dll
Registry path: HKEY_LOCAL_MACHINE\Software\Microsoft\Office\Outlook\Addins\
ProgId: Apple.DAV.Addin
Friendly name: iCloud Outlook Addin


To resolve this issue, disable or uninstall the Apple iCloud Outlook add-in, or engage the third-party vendor for other possible solutions.

To disable the iCloud Outlook Addin from within Outlook:
  1. From the File tab, select Options and in the Outlook Options dialog, select Add-Ins
  2. In the View and manage Microsoft Office Add-ins pane, under the Manage dropdown, ensure that COM Add-ins is selected, and click Go
  3. In the Add-Ins available list, uncheck the iCloud Outlook Addin, and click OK.

    Note: when you try to disable the add-in, you may receive this message:

    This add-in is installed for all users on this computer and can only be connected or disconnected by an administrator.

    If so, close Outlook and restart it using Run as Administrator, then remove the add-in. To Run as Administrator, right-click on outlook.exe or the Outlook shortcut while holding the Shift key, and choose Run as Administrator. Repeat steps 1 through 3 above, then close and restart Outlook normally.

Third-party information disclaimer

The third-party product that this article discusses is manufactured by a company that is independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of this product. 

Note This is a "FAST PUBLISH" article created directly from within the Microsoft support organization. The information contained herein is provided as-is in response to emerging issues. As a result of the speed in making it available, the materials may include typographical errors and may be revised at any time without notice. See Terms of Use for other considerations.

More Information

The iCloud Outlook Addin is registered in the following Windows Registry locations, depending on how the add-in was installed:



Disabling the iCloud Outlook Addin using the steps above changes the LoadBehavior value under these registry keys to 2 (0x00000002).