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 Fix Outlook and Office 365 Errors 2025 beneficial for users who are facing Outlook syncing issues because of corrupted PST or OST files.

Turn off Windows Defender Security Center

If the size of your .ost file is close to the limit, you could try increasing the limit on your client, restart Outlook and see if there is any difference. fix Outlook after Windows Update issues I’ve unchecked download shared folders when setting up a new Outlook profile. After performing these steps, Outlook’s all folders will be synced to the server. If this method doesn’t work for you, navigate to other solutions. Select the button below to launch a diagnostic in the Microsoft 365 admin center.

Check if two-factor authentication is turned on for your account

Once the client started using Outlook again after some time has passed the issue had come back. I ran the PSTscan tool to check for anomalies on the OST file (which it found and repaired but the issue still occurs). I’ve tried to set cache mode from 1 year all the way down to a few days.

Check Antivirus and Firewall Settings

• After you’re satisfied, turn off your firewall or antivirus program for a while.
• Windows Defender Security Center is free security software that's included with Windows 10.
• In some cases setting up a new computer replacement was the only option to fix these odd Outlook Sync issues.
• Tempted to create a Test Shared Mailbox, but thinking that wouldn't be an accurate test for inbound mail, etc. or just actually tested by the Users at all.
• We have shared five manual methods in this blog to resolve the Outlook syncing errors.
• However, I cannot find any reason why his account would do this only on our domain nothing is blocking our connection to Office 365.

After you’re satisfied, turn off your firewall or antivirus program fix MFA prompts not working for a while. If it does, you might need to include Outlook exceptions in the settings of your security program. Now, we will verify the server settings to fix the Outlook synchronization error. After the files get repaired, restart the Outlook program to ensure that the Outlook syncing issues are resolved or not. I still have it turned on on my laptop and it has not shown any issues yet. However I do not use Outlook on it as much as I do on my desktop.

Free Methods to Remove Duplicate Items in Outlook 2016

Check the software documentation to learn how to temporarily turn it off. There are various methods to resolve the Outlook sync issues, including manual and third-party solutions. Firstly, we will discuss a few manual methods to resolve this Outlook error and share the stepwise procedure of each method to successfully fix synchronization issues. Now, let us start with the manual processes to fix Outlook syncing errors. Firewalls and antivirus software might prevent you from syncing your email and calendar events. These syncing problems usually happen because of issues like a damaged Outlook profile, poor internet connection, or a corrupted OST file.