So, follow the below work offline mode stuck steps to reset Microsoft Outlook settings. After the files get repaired, restart the Outlook program to ensure that the Outlook syncing issues are resolved or not. 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.

Method 4: Recreating the Outlook Profile

However once I joined this computer back to the domain and let it sit for a few days it was also working fine. Once the client started using Outlook again after some time has passed the issue had come back. I’ve tried to set cache mode from 1 year all the way down to a few days. If your password isn't the problem, you might have a certificate error. If so, you'll see a message that says, "There is a problem with the server's security certificate. The security certificate diagnose Office activation conflicts is not from a trusted certifying authority."

Check the connectivity to your email server

• You'll also receive a mail (to the alternate email and to your admin email) from Microsoft 365 that indicates your tenant has encountered directory synchronization errors.
• It is possible for a corrupted Outlook profile to impede synchronization.
• If you're using an Outlook.com, Microsoft 365, or Exchange account, you won't have advanced mailbox settings unless the account was set up using advanced setup.
• Try the general troubleshooting solutions in Troubleshooting Mail and Calendar apps for Windows 10.
• 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.
• If you can sync your email when the firewall is turned off, you'll need to allow the Mail and Calendar apps through the firewall.

When the user is signed into their mobile app, webmail, or the guide to Office 365 sign-in errors Windows Mail app, they are able to receive email perfectly fine with those. The issue is occurring only in the Outlook program installed on Windows. To update from Azure AD Sync to Microsoft Entra Connect, see the upgrade instructions.

Methods to fix Microsoft Outlook syncing error

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. If you're using an Outlook.com, Microsoft 365, or Exchange account, you won't have advanced mailbox settings unless the account was set up using advanced setup. The client has a computer off the domain at home that his work email is tied to and he has never had any of these issues in Cache mode with that device. I’ve unchecked download shared folders when setting up a new Outlook profile. Check with your email provider for instructions about how to create an app password for your email account. The Mail and Calendar apps for Windows 10 don't support two-factor authentication.

Microsoft Outlook Sync issues

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. This software allows users to process numerous OST files at once without any size limitations. Moreover, it maintains the folder hierarchy and metaproperties of the data when processing Outlook data files.