Outlook Sync Issues Folder Filling With Conflicts: How to Diagnose

If your Outlook Sync Issues folder is filling with conflicts, your email client is detecting two or more versions of the same item that cannot be merged automatically. This typically happens when a mailbox item is modified on the server and on your local machine at nearly the same time, or when a synchronization process is interrupted. The Conflicts subfolder inside Sync Issues stores these duplicate versions so you can manually resolve them. This article explains why conflicts occur and provides a step-by-step diagnostic process to reduce or eliminate them.

Why the Sync Issues Folder Fills With Conflicts

The Sync Issues folder is a hidden system folder in Outlook that only appears when you are using Cached Exchange Mode. It contains subfolders named Conflicts, Local Failures, and Server Failures. The Conflicts subfolder stores items that Outlook could not synchronize because the same item was changed in two places at once — for example, you edited a meeting request on your phone while Outlook was syncing a server-side update to the same request.

Conflicts can also appear when:

• Your mailbox is accessed by multiple devices simultaneously.
• A network interruption occurs during a sync cycle.
• The local OST file becomes corrupted.
• An add-in interferes with Outlook sync processes.

Each conflict represents a version of the item that Outlook could not merge. The item with the most recent modification time wins the sync, and the losing version is placed in the Conflicts folder. Over time, this folder can accumulate hundreds of entries, causing confusion and making it harder to find real data.

Diagnostic Steps to Identify and Reduce Conflicts

Follow these steps in order to diagnose the root cause of frequent conflicts. Complete each step before moving to the next.

1. Open the Sync Issues Folder
   In the Outlook folder pane, scroll to the bottom of your mailbox folders. If you see a folder named Sync Issues, expand it. If you do not see it, click the three dots (More) at the bottom of the folder pane and select Folders. Look for Sync Issues under your mailbox root. Open the Conflicts subfolder and note the number of items and the type of items (email, calendar, contacts).
2. Examine a Sample Conflict Item
   Double-click any item in the Conflicts folder. Compare its subject, body, and attachments with the same item in your main mailbox folder. Note whether the conflict item is a duplicate of a recent change or an older version. This tells you whether the conflict is from a current sync problem or a backlog.
3. Check the Sync Status Using the Outlook Connection Status Dialog
   Hold the Ctrl key and right-click the Outlook icon in the system tray (notification area). Select Connection Status. Look at the Status column for your mailbox. If you see Disconnected or Trying to Connect, the sync is unstable. If you see Connected (Cached), the sync is healthy. Any other status indicates a network or server problem.
4. Disable Cached Exchange Mode
   Go to File > Account Settings > Account Settings. Select your Exchange account and click Change. Under Offline Settings, uncheck Use Cached Exchange Mode. Click Next and restart Outlook. If conflicts stop appearing, the issue is related to the local cache. Re-enable Cached Exchange Mode after testing.
5. Repair the OST File with Scanpst.exe
   Close Outlook. Press Windows key + R, type scanpst.exe, and press Enter. Browse to your OST file. The default location is C:\Users\[YourUsername]\AppData\Local\Microsoft\Outlook. Select the OST file and click Start. Let the tool scan and repair errors. Restart Outlook and check the Conflicts folder again.
6. Create a New Outlook Profile
   Go to Control Panel > Mail > Show Profiles. Click Add and name the profile. Enter your email address and password. Set the new profile as the default. Open Outlook with the new profile. If conflicts stop, your original profile was corrupted. You can migrate data from the old profile using File > Open & Export > Import/Export.

If Conflicts Persist After Diagnosis

Conflict items are actual duplicates that I need to keep

If the conflict items contain unique data you want to keep, you must manually merge them. Open the conflict item and the original item side by side. Copy the unique content from the conflict item into the original item. Delete the conflict item from the Conflicts folder. Do this for each item you need to preserve.

Conflicts appear only on one specific device

The device may have a corrupted OST file or an outdated Outlook version. Run the Inbox Repair Tool on that device. Also update Outlook to the latest version via File > Office Account > Update Options > Update Now. If the device is a mobile phone, remove and re-add the Exchange account on the phone.

Conflicts contain only calendar items or only contacts

This points to a specific sync issue with that folder type. In Outlook, right-click the affected folder (Calendar or Contacts) and select Properties. Go to the Synchronization tab. Click Reset Folder. This forces a full resync of that folder. Check the Conflicts folder after the resync completes.

Conflicts folder contains hundreds of items from months ago

Outlook may have accumulated conflicts over time without being cleared. Select all items in the Conflicts folder (Ctrl + A) and press Delete. This does not delete the original items in your mailbox — it only removes the copies that Outlook could not merge. After clearing the folder, monitor for new conflicts over the next week.

Item	Local OST (Cached Exchange Mode)	Online Mode (No Cache)
Description	Stores a local copy of mailbox items; syncs changes periodically	Directly accesses mailbox on the Exchange server; no local copy
Conflict behavior	Conflicts appear when local and server changes collide; items stored in Sync Issues folder	Conflicts are resolved immediately by the server; no local Sync Issues folder
Performance	Faster offline access; slower first sync; uses disk space	Slower performance on slow networks; no offline access
Best for	Users on slow or unreliable connections; need offline access	Users on fast, stable connections; do not need offline access

You can now identify the cause of conflicts in your Sync Issues folder and apply the appropriate fix. After clearing the Conflicts folder, monitor it for one week. If conflicts reappear, disable Cached Exchange Mode temporarily to confirm the root cause. For advanced diagnostics, enable Outlook logging via File > Options > Advanced > Enable troubleshooting logging, then review the log file in %temp%\Outlook Logging for sync error codes.