Sometimes, Outlook sync issues can arise because of poor internet connection. If you are still facing this issue, kindly follow the solutions below to fix the sync issues in Office 365 Sync Errors Fix Outlook. If users are facing syncing issues in Outlook due to corrupt Outlook data files, they must choose a professional tool, like Shoviv OST to PST Converter Tool.

Turn off Windows Defender Security Center

If there's a feature you think is missing from the Mail and Outlook Login Issues Troubleshooting Calendar apps, or if a feature in isn't working properly, you can provide feedback directly to the Mail and Calendar team. Two-factor authentication helps protect your account by making it more difficult for someone else to sign in. It verifies your identity using your password and a contact method (also known as security info). If you would like to ask me another question in the future or follow up on your current question, you can add me as a favorite Expert.

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

Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support. These are the only two I've seen have this issue and I was wondering if you've seen this and figured out a 'fix'? 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.

Check Antivirus and Firewall Settings

• If you're using an Exchange account that requires advanced settings, you'll need to remove the account and add it again using advanced settings.
• After you’re satisfied, turn off your firewall or antivirus program for a while.
• In the notification bar at the top of the app, select Fix account.
• Windows Defender Security Center is free security software that's included with Windows 10.
• This blog talks about the causes behind Outlook synchronization errors and a few solutions to fix 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.

If you can sync your email when the firewall is turned off, you'll need to allow the mailbox not updating on IMAP Mail and Calendar apps through the firewall. Windows Defender Security Center is free security software that's included with Windows 10. If you haven't installed alternative security software, you should temporarily turn off Windows Defender Security Center.

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.