If the connection is poor, consider restarting your modem/router or moving to a more reliable network. You will need to have the correct privileges set on your Azure account in order to set up the M365 sync. We're in the process of migrating from On-Premise Exchange to O365. I have a couple of Users and a Shared Mailbox that were migrated and both Users are experiencing issues with the Shared Mailbox updating on a regular basis. Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support. Additionally, you might want to make a new profile and make it the default to see if it fixes the problem.

Common Causes of Sync Issues in Outlook

Knowing the reasons behind the Outlook sync issues will help us to fix this problem and prevent issues in communication and workflow. There can be several reasons for the Outlook synchronization error. Before we know the solutions, we will understand a few common causes of the Outlook sync problem. Find out what to do if you are having issues with syncing users or groups from Microsoft 365. It is possible for a corrupted Outlook profile to impede synchronization.

Fixing problems with directory synchronization for Microsoft 365

Another which is shown below, is a user opens a new message, or replies to one, and lets it sit for a while. When they go back to the message and press work offline mode stuck send they get an error that the message has been deleted. Ive repaired the OST and changed cache mode to only cache 1 year.

• Sync failure alerts do not always include a full summary or attachment, you can run a test sync to obtain this data.
• If the connection is poor, consider restarting your modem/router or moving to a more reliable network.
• Outlook’s ability to connect to the mail server may be blocked by firewalls or antivirus software.
• After you’re satisfied, turn off your firewall or antivirus program for a while.
• Another which is shown below, is a user opens a new message, or replies to one, and lets it sit for a while.
• The M365 sync establishes a synced dataset based on your M365 data and the filtering configuration of your sync.

Use the Microsoft Support and Recovery Assistant

Outlook sync issues can be because of corrupted Outlook OST or PST files. Therefore, now we will know the steps to repair the Outlook data file. The most common reason for missing users is that you've run a Test Sync, instead of a Manual Sync. If that doesn't resolve your missing users issue, please follow our guide to troubleshooting missing users below. With directory synchronization, you can continue to manage users and groups on-premises and synchronize additions, deletions, and changes to the cloud.

How to Fix Outlook Sync Issues in Windows?

The sync will fail if it can't find any users that comply with your filtering preferences or the system's requirements for user records. The system requires that users have a first name, last name and a valid email address that conforms with your domain lock if enabled. The sync does not delete users but rather sets them to inactive. The idea is to provide a troubleshoot Outlook synchronizing folders error recycle bin of users who you can delete when you no longer need them.





If this method doesn’t work for you, navigate to other solutions. Both of our authentication methods can fail if the Enterprise Applications entry for the sync in Azure AD is deleted or if it has had its permissions modified. To get the sync working you will either need to delete users or have the user limit on your account increased. If you don't wish an inactive user to be made active by the M365 sync, you can add the user's email address to the sync forbid list. You can do this in the Microsoft Outlook sync help from FixTechGuide 365 Sync Wizard on the configuration page of your platform settings. Once you have completed the steps to fix Outlook sync errors, kindly check if the error has been fixed or not.

What should I do if my sync fails because it can't find any users?

The error message in the Summary sheet of the Sync Summary spreadsheet attachment can also highlight the reason for this. This means that the authentication setup for your sync is no longer valid. This can happen for the a number reasons particularly if your sync authenticates using Delegated Permissions.



This blog talks about the causes behind Outlook synchronization errors and a few solutions to fix Outlook sync issues. We have shared five manual methods in this blog to resolve the Outlook syncing errors. Apart from this, we also discuss the Shoviv OST to PST Converter Tool, a professional way to repair, recover, and convert Outlook data files. This solution will be beneficial for users who are facing Outlook syncing issues because of corrupted PST or OST files. Users can also try its free demo version in their system and process the first 50 items from each folder freely. Always make sure your profile and settings are set up correctly, your software is up to date, and your connection is steady.