Outlook Error Codes

Fix Outlook IMAP Sync Error 800CCC0F-0-0-560

Chanuka Geekiyanage Oct 23, 2026 869 views

Question details

Users need a solution to stop Outlook IMAP synchronization problems that repeatedly revert messages to an unread status and generate massive amounts of Sync Issues messages.

How to Fix Outlook IMAP Sync Error 800CCC0F-0-0-560

Product: Microsoft Outlook
Device & OS: Windows
Scenario: Synchronizing an IMAP email account where Outlook fails to close properly, causing repetitive sync loops and incorrect read/unread status.
Observed behavior: Outlook repeatedly marks read messages as unread, generates a large number of Sync Issues logs, and gets stuck synchronizing IMAP folders.

Before you start

Close Microsoft Outlook and all other Office applications. Because the primary fix requires modifying the Windows Registry, be sure to create a backup of your registry before proceeding.

Solution 1Recommended

Apply the AllowLOGOUTWithoutOK Registry Workaround

Adding a specific DWORD value to the Windows Registry forces Outlook to handle IMAP logouts correctly, breaking the synchronization loop.

Microsoft has identified that Outlook may not close properly with an IMAP account, which directly causes these synchronization problems. This registry edit acts as a direct workaround.

Open the Registry Editor

Press the Windows key + R, type 'regedit' into the Run dialog, and press Enter to launch the Registry Editor.

Navigate to the Outlook IMAP Key

Navigate to the following path: HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Outlook\IMAP. Note that '16.0' refers to Outlook 2016, 2019, and Microsoft 365.

Create the New DWORD Value

Right-click in the right pane, select New > DWORD (32-bit) Value, and name it exactly 'AllowLOGOUTWithoutOK'.

Modify the Value Data

Double-click 'AllowLOGOUTWithoutOK', set the Value data to '1', and click OK. Close the Registry Editor and restart your computer.

Apply the AllowLOGOUTWithoutOK Registry Workaround

Registry Warning: Modifying the registry incorrectly can cause system issues. Always back up the specific registry key or create a system restore point before making changes.

Solution 2

Clear Problematic Messages in the Sync Issues Folder

Reviewing and moving or deleting stuck messages can clear the local synchronization queue and restore normal IMAP folder syncing.

Solution 3

Adjust the 'Mail to keep offline' Sync Slider

Changing the synchronization slider forces Outlook to update the local cache, which can resolve folder syncing hangs.

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Frequently Asked Questions

Why do my read emails keep changing back to unread in Outlook?

This commonly happens with IMAP accounts when Outlook fails to close the server connection properly. As a result, the server's previous 'unread' status overwrites your local client's 'read' status during the next synchronization cycle.

Where can I find the Sync Issues folder in Outlook?

The Sync Issues folder is hidden by default in the standard Mail view. You can reveal it by pressing Ctrl + 6, which switches your navigation pane to the 'Folder List' view, displaying all hidden system folders under your account.

Does the AllowLOGOUTWithoutOK registry fix work for older versions of Outlook?

The registry path provided includes '16.0', which applies specifically to Outlook 2016, 2019, and Microsoft 365. If you are using an older version, the version number in the path will differ (e.g., use '15.0' for Outlook 2013 or '14.0' for Outlook 2010).

How long does it take for Outlook to update the local IMAP cache?

The time it takes depends entirely on the size of your mailbox and your internet connection speed. If you adjust your sync slider to 'All', Outlook will download the entire mailbox history, which could take anywhere from a few minutes to several hours.

Microsoft Office Error Codes