Incorrect Outlook settings can also be one of the reasons behind Outlook synchronization errors. The Support and Recovery Assistant, a tool provided by Microsoft, can identify and resolve common Outlook problems. It is capable of automatically Office 365 sync problems and login fixes identifying problems with account setups, sync, and other typical mistakes. To solve your Outlook issues, download the application from the Microsoft website and follow the directions. Outlook’s ability to connect to the mail server may be blocked by firewalls or antivirus software.

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. disable faulty add-ins in Outlook 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

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

• I ran the PSTscan tool to check for anomalies on the OST file (which it found and repaired but the issue still occurs).
• It is capable of automatically identifying problems with account setups, sync, and other typical mistakes.
• Outlook sync issues can be because of corrupted Outlook OST or PST files.
• Knowing the reasons behind the Outlook sync issues will help us to fix this problem and prevent issues in communication and workflow.
• If two-factor authentication is turned on for your account, you'll need to create an app password for that account.
• Third-party firewalls or antivirus software might prevent you from syncing your email and calendar events.
• Always make sure your profile and settings are set up correctly, your software is up to date, and your connection is steady.

If you can sync your email when the firewall is turned off, you'll need to allow the Outlook Not Sending or Receiving Email 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

Here is the strange part I tried to remove the computer from the domain and have Outlook run from a local account for a few days. I’ve been in contact with Microsoft they had me migrate his account\data to another server this did not fix it. I’ve tried the Microsoft office uninstall tool provided by Microsoft (which deletes more items then just control panel uninstall).